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Patch series "mm/memory_hotplug: allow to specify a default online_type", v3.
Distributions nowadays use udev rules ([1] [2]) to specify if and how to
online hotplugged memory. The rules seem to get more complex with many
special cases. Due to the various special cases,
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE cannot be used. All memory hotplug
is handled via udev rules.
Every time we hotplug memory, the udev rule will come to the same
conclusion. Especially Hyper-V (but also soon virtio-mem) add a lot of
memory in separate memory blocks and wait for memory to get onlined by
user space before continuing to add more memory blocks (to not add memory
faster than it is getting onlined). This of course slows down the whole
memory hotplug process.
To make the job of distributions easier and to avoid udev rules that get
more and more complicated, let's extend the mechanism provided by
- /sys/devices/system/memory/auto_online_blocks
- "memhp_default_state=" on the kernel cmdline
to be able to specify also "online_movable" as well as "online_kernel"
=== Example /usr/libexec/config-memhotplug ===
#!/bin/bash
VIRT=`systemd-detect-virt --vm`
ARCH=`uname -p`
sense_virtio_mem() {
if [ -d "/sys/bus/virtio/drivers/virtio_mem/" ]; then
DEVICES=`find /sys/bus/virtio/drivers/virtio_mem/ -maxdepth 1 -type l | wc -l`
if [ $DEVICES != "0" ]; then
return 0
fi
fi
return 1
}
if [ ! -e "/sys/devices/system/memory/auto_online_blocks" ]; then
echo "Memory hotplug configuration support missing in the kernel"
exit 1
fi
if grep "memhp_default_state=" /proc/cmdline > /dev/null; then
echo "Memory hotplug configuration overridden in kernel cmdline (memhp_default_state=)"
exit 1
fi
if [ $VIRT == "microsoft" ]; then
echo "Detected Hyper-V on $ARCH"
# Hyper-V wants all memory in ZONE_NORMAL
ONLINE_TYPE="online_kernel"
elif sense_virtio_mem; then
echo "Detected virtio-mem on $ARCH"
# virtio-mem wants all memory in ZONE_NORMAL
ONLINE_TYPE="online_kernel"
elif [ $ARCH == "s390x" ] || [ $ARCH == "s390" ]; then
echo "Detected $ARCH"
# standby memory should not be onlined automatically
ONLINE_TYPE="offline"
elif [ $ARCH == "ppc64" ] || [ $ARCH == "ppc64le" ]; then
echo "Detected" $ARCH
# PPC64 onlines all hotplugged memory right from the kernel
ONLINE_TYPE="offline"
elif [ $VIRT == "none" ]; then
echo "Detected bare-metal on $ARCH"
# Bare metal users expect hotplugged memory to be unpluggable. We assume
# that ZONE imbalances on such enterpise servers cannot happen and is
# properly documented
ONLINE_TYPE="online_movable"
else
# TODO: Hypervisors that want to unplug DIMMs and can guarantee that ZONE
# imbalances won't happen
echo "Detected $VIRT on $ARCH"
# Usually, ballooning is used in virtual environments, so memory should go to
# ZONE_NORMAL. However, sometimes "movable_node" is relevant.
ONLINE_TYPE="online"
fi
echo "Selected online_type:" $ONLINE_TYPE
# Configure what to do with memory that will be hotplugged in the future
echo $ONLINE_TYPE 2>/dev/null > /sys/devices/system/memory/auto_online_blocks
if [ $? != "0" ]; then
echo "Memory hotplug cannot be configured (e.g., old kernel or missing permissions)"
# A backup udev rule should handle old kernels if necessary
exit 1
fi
# Process all already pluggedd blocks (e.g., DIMMs, but also Hyper-V or virtio-mem)
if [ $ONLINE_TYPE != "offline" ]; then
for MEMORY in /sys/devices/system/memory/memory*; do
STATE=`cat $MEMORY/state`
if [ $STATE == "offline" ]; then
echo $ONLINE_TYPE > $MEMORY/state
fi
done
fi
=== Example /usr/lib/systemd/system/config-memhotplug.service ===
[Unit]
Description=Configure memory hotplug behavior
DefaultDependencies=no
Conflicts=shutdown.target
Before=sysinit.target shutdown.target
After=systemd-modules-load.service
ConditionPathExists=|/sys/devices/system/memory/auto_online_blocks
[Service]
ExecStart=/usr/libexec/config-memhotplug
Type=oneshot
TimeoutSec=0
RemainAfterExit=yes
[Install]
WantedBy=sysinit.target
=== Example modification to the 40-redhat.rules [2] ===
: diff --git a/40-redhat.rules b/40-redhat.rules-new
: index 2c690e5..168fd03 100644
: --- a/40-redhat.rules
: +++ b/40-redhat.rules-new
: @@ -6,6 +6,9 @@ SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}
: # Memory hotadd request
: SUBSYSTEM!="memory", GOTO="memory_hotplug_end"
: ACTION!="add", GOTO="memory_hotplug_end"
: +# memory hotplug behavior configured
: +PROGRAM=="grep online /sys/devices/system/memory/auto_online_blocks", GOTO="memory_hotplug_end"
: +
: PROGRAM="/bin/uname -p", RESULT=="s390*", GOTO="memory_hotplug_end"
:
: ENV{.state}="online"
===
[1] https://github.com/lnykryn/systemd-rhel/pull/281
[2] https://github.com/lnykryn/systemd-rhel/blob/staging/rules/40-redhat.rules
This patch (of 8):
The name is misleading and it's not really clear what is "kept". Let's
just name it like the online_type name we expose to user space ("online").
Add some documentation to the types.
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Yumei Huang <yuhuang@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Link: http://lkml.kernel.org/r/20200319131221.14044-1-david@redhat.com
Link: http://lkml.kernel.org/r/20200317104942.11178-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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No functional change.
[bhe@redhat.com: move functions into CONFIG_MEMORY_HOTPLUG ifdeffery scope]
Link: http://lkml.kernel.org/r/20200316045804.GC3486@MiWiFi-R3L-srv
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Link: http://lkml.kernel.org/r/20200312124414.439-6-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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And tell check_pfn_span() gating the porper alignment and size of hot
added memory region.
And also move the code comments from inside section_deactivate() to being
above it. The code comments are reasonable for the whole function, and
the moving makes code cleaner.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Link: http://lkml.kernel.org/r/20200312124414.439-5-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Currently, to support subsection aligned memory region adding for pmem,
subsection map is added to track which subsection is present.
However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means
subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the
classic sparse, it's meaningless. Even worse, it may confuse people when
checking code related to the classic sparse.
About the classic sparse which doesn't support subsection hotplug, Dan
said it's more because the effort and maintenance burden outweighs the
benefit. Besides, the current 64 bit ARCHes all enable
SPARSEMEM_VMEMMAP_ENABLE by default.
Combining the above reasons, no need to provide subsection map and the
relevant handling for the classic sparse. Let's remove them.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Link: http://lkml.kernel.org/r/20200312124414.439-4-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Factor out the code which clear subsection map of one memory region from
section_deactivate() into clear_subsection_map().
And also add helper function is_subsection_map_empty() to check if the
current subsection map is empty or not.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Link: http://lkml.kernel.org/r/20200312124414.439-3-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "mm/hotplug: Only use subsection map for VMEMMAP", v4.
Memory sub-section hotplug was added to fix the issue that nvdimm could be
mapped at non-section aligned starting address. A subsection map is added
into struct mem_section_usage to implement it.
However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means
subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the
classic sparse, subsection map is meaningless and confusing.
About the classic sparse which doesn't support subsection hotplug, Dan
said it's more because the effort and maintenance burden outweighs the
benefit. Besides, the current 64 bit ARCHes all enable
SPARSEMEM_VMEMMAP_ENABLE by default.
This patch (of 5):
Factor out the code that fills the subsection map from section_activate()
into fill_subsection_map(), this makes section_activate() cleaner and
easier to follow.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/20200312124414.439-2-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Let's drop the basically unused section stuff and simplify. The logic now
matches the logic in __remove_pages().
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Link: http://lkml.kernel.org/r/20200228095819.10750-3-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In commit 52fb87c81f11 ("mm/memory_hotplug: cleanup __remove_pages()"), we
cleaned up __remove_pages(), and introduced a shorter variant to calculate
the number of pages to the next section boundary.
Turns out we can make this calculation easier to read. We always want to
have the number of pages (> 0) to the next section boundary, starting from
the current pfn.
We'll clean up __remove_pages() in a follow-up patch and directly make use
of this computation.
Suggested-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Link: http://lkml.kernel.org/r/20200228095819.10750-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In commit 357b4da50a62 ("x86: respect memory size limiting via mem=
parameter") a global varialbe max_mem_size is added to store the value
parsed from 'mem= ', then checked when memory region is added. This truly
stops those DIMMs from being added into system memory during boot-time.
However, it also limits the later memory hotplug functionality. Any DIMM
can't be hotplugged any more if its region is beyond the max_mem_size. We
will get errors like:
[ 216.387164] acpi PNP0C80:02: add_memory failed
[ 216.389301] acpi PNP0C80:02: acpi_memory_enable_device() error
[ 216.392187] acpi PNP0C80:02: Enumeration failure
This will cause issue in a known use case where 'mem=' is added to the
hypervisor. The memory that lies after 'mem=' boundary will be assigned
to KVM guests. After commit 357b4da50a62 merged, memory can't be extended
dynamically if system memory on hypervisor is not sufficient.
So fix it by also checking if it's during boot-time restricting to add
memory. Otherwise, skip the restriction.
And also add this use case to document of 'mem=' kernel parameter.
Fixes: 357b4da50a62 ("x86: respect memory size limiting via mem= parameter")
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: http://lkml.kernel.org/r/20200204050643.20925-1-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Since commit c5e79ef561b0 ("mm/memory_hotplug.c: don't allow to
online/offline memory blocks with holes") we disallow to offline any
memory with holes. As all boot memory is online and hotplugged memory
cannot contain holes, we never online memory with holes.
This present check can be dropped.
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: http://lkml.kernel.org/r/20200127110424.5757-4-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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pages_correctly_probed() is a leftover from ancient times. It dates back
to commit 3947be1969a9 ("[PATCH] memory hotplug: sysfs and add/remove
functions"), where Pg_reserved checks were added as a sfety net:
/*
* The probe routines leave the pages reserved, just
* as the bootmem code does. Make sure they're still
* that way.
*/
The checks were refactored quite a bit over the years, especially in
commit b77eab7079d9 ("mm/memory_hotplug: optimize probe routine"), where
checks for present, valid, and online sections were added.
Hotplugged memory is added via add_memory(), which will create the full
memmap for the hotplugged memory, and mark all sections valid and present.
Only full memory blocks are onlined/offlined, so we also cannot have an
inconsistency in that regard (especially, memory blocks with some sections
being online and some being offline).
1. Boot memory always starts online. Since commit c5e79ef561b0
("mm/memory_hotplug.c: don't allow to online/offline memory blocks with
holes") we disallow to offline any memory with holes. Therefore, we
never online memory with holes. Present and validity checks are
superfluous.
2. Only complete memory blocks are onlined/offlined (and especially,
the state - online or offline - is stored for whole memory blocks).
Besides the core, only arch/powerpc/platforms/powernv/memtrace.c
manually calls offline_pages() and fiddels with memory block states.
But it also only offlines complete memory blocks.
3. To make any of these conditions trigger, something would have to be
terribly messed up in the core. (e.g., online/offline only some
sections of a memory block).
4. Memory unplug properly makes sure that all sysfs attributes were
removed (and therefore, that all threads left the sysfs handlers). We
don't have to worry about zombie devices at this point.
5. The valid_section_nr(section_nr) check is actually dead code, as it
would never have been reached due to the WARN_ON_ONCE(!pfn_valid(pfn)).
No wonder we haven't seen any of these errors in a long time (or even
ever, according to my search). Let's just get rid of them. Now, all
checks that could hinder onlining and offlining are completely
contained in online_pages()/offline_pages().
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Link: http://lkml.kernel.org/r/20200127110424.5757-3-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "mm: drop superfluous section checks when onlining/offlining".
Let's drop some superfluous section checks on the onlining/offlining path.
This patch (of 3):
Since commit c5e79ef561b0 ("mm/memory_hotplug.c: don't allow to
online/offline memory blocks with holes") we have a generic check in
offline_pages() that disallows offlining memory blocks with holes.
Memory blocks with missing sections are just another variant of these type
of blocks. We can stop checking (and especially storing) present
sections. A proper error message is now printed why offlining failed.
section_count was initially introduced in commit 07681215975e ("Driver
core: Add section count to memory_block struct") in order to detect when
it is okay to remove a memory block. It was used in commit 26bbe7ef6d5c
("drivers/base/memory.c: prohibit offlining of memory blocks with missing
sections") to disallow offlining memory blocks with missing sections. As
we refactored creation/removal of memory devices and have a proper check
for holes in place, we can drop the section_count.
This also removes a leftover comment regarding the mem_sysfs_mutex, which
was removed in commit 848e19ad3c33 ("drivers/base/memory.c: drop the
mem_sysfs_mutex").
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Link: http://lkml.kernel.org/r/20200127110424.5757-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add uffd tests for write protection.
Instead of introducing new tests for it, let's simply squashing uffd-wp
tests into existing uffd-missing test cases. Changes are:
(1) Bouncing tests
We do the write-protection in two ways during the bouncing test:
- By using UFFDIO_COPY_MODE_WP when resolving MISSING pages: then
we'll make sure for each bounce process every single page will be
at least fault twice: once for MISSING, once for WP.
- By direct call UFFDIO_WRITEPROTECT on existing faulted memories:
To further torture the explicit page protection procedures of
uffd-wp, we split each bounce procedure into two halves (in the
background thread): the first half will be MISSING+WP for each
page as explained above. After the first half, we write protect
the faulted region in the background thread to make sure at least
half of the pages will be write protected again which is the first
half to test the new UFFDIO_WRITEPROTECT call. Then we continue
with the 2nd half, which will contain both MISSING and WP faulting
tests for the 2nd half and WP-only faults from the 1st half.
(2) Event/Signal test
Mostly previous tests but will do MISSING+WP for each page. For
sigbus-mode test we'll need to provide standalone path to handle the
write protection faults.
For all tests, do statistics as well for uffd-wp pages.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-20-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Introduce uffd_stats structure for statistics of the self test, at the
same time refactor the code to always pass in the uffd_stats for either
read() or poll() typed fault handling threads instead of using two
different ways to return the statistic results. No functional change.
With the new structure, it's very easy to introduce new statistics.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-19-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Only declare _UFFDIO_WRITEPROTECT if the user specified
UFFDIO_REGISTER_MODE_WP and if all the checks passed. Then when the user
registers regions with shmem/hugetlbfs we won't expose the new ioctl to
them. Even with complete anonymous memory range, we'll only expose the
new WP ioctl bit if the register mode has MODE_WP.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-18-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add documentation about the write protection support.
[peterx@redhat.com: rewrite in rst format; fixups here and there]
Signed-off-by: Martin Cracauer <cracauer@cons.org>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-17-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
It does not make sense to try to wake up any waiting thread when we're
write-protecting a memory region. Only wake up when resolving a write
protected page fault.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-16-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Now it's safe to enable write protection in userfaultfd API
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220163112.11409-15-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Introduce the new uffd-wp APIs for userspace.
Firstly, we'll allow to do UFFDIO_REGISTER with write protection tracking
using the new UFFDIO_REGISTER_MODE_WP flag. Note that this flag can
co-exist with the existing UFFDIO_REGISTER_MODE_MISSING, in which case the
userspace program can not only resolve missing page faults, and at the
same time tracking page data changes along the way.
Secondly, we introduced the new UFFDIO_WRITEPROTECT API to do page level
write protection tracking. Note that we will need to register the memory
region with UFFDIO_REGISTER_MODE_WP before that.
[peterx@redhat.com: write up the commit message]
[peterx@redhat.com: remove useless block, write commit message, check against
VM_MAYWRITE rather than VM_WRITE when register]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-14-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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Add API to enable/disable writeprotect a vma range. Unlike mprotect, this
doesn't split/merge vmas.
[peterx@redhat.com:
- use the helper to find VMA;
- return -ENOENT if not found to match mcopy case;
- use the new MM_CP_UFFD_WP* flags for change_protection
- check against mmap_changing for failures
- replace find_dst_vma with vma_find_uffd]
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220163112.11409-13-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Don't collapse the huge PMD if there is any userfault write protected
small PTEs. The problem is that the write protection is in small page
granularity and there's no way to keep all these write protection
information if the small pages are going to be merged into a huge PMD.
The same thing needs to be considered for swap entries and migration
entries. So do the check as well disregarding khugepaged_max_ptes_swap.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-12-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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For either swap and page migration, we all use the bit 2 of the entry to
identify whether this entry is uffd write-protected. It plays a similar
role as the existing soft dirty bit in swap entries but only for keeping
the uffd-wp tracking for a specific PTE/PMD.
Something special here is that when we want to recover the uffd-wp bit
from a swap/migration entry to the PTE bit we'll also need to take care of
the _PAGE_RW bit and make sure it's cleared, otherwise even with the
_PAGE_UFFD_WP bit we can't trap it at all.
In change_pte_range() we do nothing for uffd if the PTE is a swap entry.
That can lead to data mismatch if the page that we are going to write
protect is swapped out when sending the UFFDIO_WRITEPROTECT. This patch
also applies/removes the uffd-wp bit even for the swap entries.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-11-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Adding these missing helpers for uffd-wp operations with pmd
swap/migration entries.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-10-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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UFFD_EVENT_FORK support for uffd-wp should be already there, except that
we should clean the uffd-wp bit if uffd fork event is not enabled. Detect
that to avoid _PAGE_UFFD_WP being set even if the VMA is not being tracked
by VM_UFFD_WP. Do this for both small PTEs and huge PMDs.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-9-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Firstly, introduce two new flags MM_CP_UFFD_WP[_RESOLVE] for
change_protection() when used with uffd-wp and make sure the two new flags
are exclusively used. Then,
- For MM_CP_UFFD_WP: apply the _PAGE_UFFD_WP bit and remove _PAGE_RW
when a range of memory is write protected by uffd
- For MM_CP_UFFD_WP_RESOLVE: remove the _PAGE_UFFD_WP bit and recover
_PAGE_RW when write protection is resolved from userspace
And use this new interface in mwriteprotect_range() to replace the old
MM_CP_DIRTY_ACCT.
Do this change for both PTEs and huge PMDs. Then we can start to identify
which PTE/PMD is write protected by general (e.g., COW or soft dirty
tracking), and which is for userfaultfd-wp.
Since we should keep the _PAGE_UFFD_WP when doing pte_modify(), add it
into _PAGE_CHG_MASK as well. Meanwhile, since we have this new bit, we
can be even more strict when detecting uffd-wp page faults in either
do_wp_page() or wp_huge_pmd().
After we're with _PAGE_UFFD_WP, a special case is when a page is both
protected by the general COW logic and also userfault-wp. Here the
userfault-wp will have higher priority and will be handled first. Only
after the uffd-wp bit is cleared on the PTE/PMD will we continue to handle
the general COW. These are the steps on what will happen with such a
page:
1. CPU accesses write protected shared page (so both protected by
general COW and uffd-wp), blocked by uffd-wp first because in
do_wp_page we'll handle uffd-wp first, so it has higher priority
than general COW.
2. Uffd service thread receives the request, do UFFDIO_WRITEPROTECT
to remove the uffd-wp bit upon the PTE/PMD. However here we
still keep the write bit cleared. Notify the blocked CPU.
3. The blocked CPU resumes the page fault process with a fault
retry, during retry it'll notice it was not with the uffd-wp bit
this time but it is still write protected by general COW, then
it'll go though the COW path in the fault handler, copy the page,
apply write bit where necessary, and retry again.
4. The CPU will be able to access this page with write bit set.
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-8-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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change_protection() was used by either the NUMA or mprotect() code,
there's one parameter for each of the callers (dirty_accountable and
prot_numa). Further, these parameters are passed along the calls:
- change_protection_range()
- change_p4d_range()
- change_pud_range()
- change_pmd_range()
- ...
Now we introduce a flag for change_protect() and all these helpers to
replace these parameters. Then we can avoid passing multiple parameters
multiple times along the way.
More importantly, it'll greatly simplify the work if we want to introduce
any new parameters to change_protection(). In the follow up patches, a
new parameter for userfaultfd write protection will be introduced.
No functional change at all.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-7-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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This allows UFFDIO_COPY to map pages write-protected.
[peterx@redhat.com: switch to VM_WARN_ON_ONCE in mfill_atomic_pte; add brackets
around "dst_vma->vm_flags & VM_WRITE"; fix wordings in comments and
commit messages]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-6-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Implement helpers methods to invoke userfaultfd wp faults more
selectively: not only when a wp fault triggers on a vma with vma->vm_flags
VM_UFFD_WP set, but only if the _PAGE_UFFD_WP bit is set in the pagetable
too.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-5-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Accurate userfaultfd WP tracking is possible by tracking exactly which
virtual memory ranges were writeprotected by userland. We can't relay
only on the RW bit of the mapped pagetable because that information is
destroyed by fork() or KSM or swap. If we were to relay on that, we'd
need to stay on the safe side and generate false positive wp faults for
every swapped out page.
[peterx@redhat.com: append _PAGE_UFD_WP to _PAGE_CHG_MASK]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-4-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
There are several cases write protection fault happens. It could be a
write to zero page, swaped page or userfault write protected page. When
the fault happens, there is no way to know if userfault write protect the
page before. Here we just blindly issue a userfault notification for vma
with VM_UFFD_WP regardless if app write protects it yet. Application
should be ready to handle such wp fault.
In the swapin case, always swapin as readonly. This will cause false
positive userfaults. We need to decide later if to eliminate them with a
flag like soft-dirty in the swap entry (see _PAGE_SWP_SOFT_DIRTY).
hugetlbfs wouldn't need to worry about swapouts but and tmpfs would be
handled by a swap entry bit like anonymous memory.
The main problem with no easy solution to eliminate the false positives,
will be if/when userfaultfd is extended to real filesystem pagecache.
When the pagecache is freed by reclaim we can't leave the radix tree
pinned if the inode and in turn the radix tree is reclaimed as well.
The estimation is that full accuracy and lack of false positives could be
easily provided only to anonymous memory (as long as there's no fork or as
long as MADV_DONTFORK is used on the userfaultfd anonymous range) tmpfs
and hugetlbfs, it's most certainly worth to achieve it but in a later
incremental patch.
[peterx@redhat.com: don't conditionally drop FAULT_FLAG_WRITE in do_swap_page]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-3-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "userfaultfd: write protection support", v6.
Overview
========
The uffd-wp work was initialized by Shaohua Li [1], and later continued by
Andrea [2]. This series is based upon Andrea's latest userfaultfd tree,
and it is a continuous works from both Shaohua and Andrea. Many of the
follow up ideas come from Andrea too.
Besides the old MISSING register mode of userfaultfd, the new uffd-wp
support provides another alternative register mode called
UFFDIO_REGISTER_MODE_WP that can be used to listen to not only missing
page faults but also write protection page faults, or even they can be
registered together. At the same time, the new feature also provides a
new userfaultfd ioctl called UFFDIO_WRITEPROTECT which allows the
userspace to write protect a range or memory or fixup write permission of
faulted pages.
Please refer to the document patch "userfaultfd: wp:
UFFDIO_REGISTER_MODE_WP documentation update" for more information on the
new interface and what it can do.
The major workflow of an uffd-wp program should be:
1. Register a memory region with WP mode using UFFDIO_REGISTER_MODE_WP
2. Write protect part of the whole registered region using
UFFDIO_WRITEPROTECT, passing in UFFDIO_WRITEPROTECT_MODE_WP to
show that we want to write protect the range.
3. Start a working thread that modifies the protected pages,
meanwhile listening to UFFD messages.
4. When a write is detected upon the protected range, page fault
happens, a UFFD message will be generated and reported to the
page fault handling thread
5. The page fault handler thread resolves the page fault using the
new UFFDIO_WRITEPROTECT ioctl, but this time passing in
!UFFDIO_WRITEPROTECT_MODE_WP instead showing that we want to
recover the write permission. Before this operation, the fault
handler thread can do anything it wants, e.g., dumps the page to
a persistent storage.
6. The worker thread will continue running with the correctly
applied write permission from step 5.
Currently there are already two projects that are based on this new
userfaultfd feature.
QEMU Live Snapshot: The project provides a way to allow the QEMU
hypervisor to take snapshot of VMs without
stopping the VM [3].
LLNL umap library: The project provides a mmap-like interface and
"allow to have an application specific buffer of
pages cached from a large file, i.e. out-of-core
execution using memory map" [4][5].
Before posting the patchset, this series was smoke tested against QEMU
live snapshot and the LLNL umap library (by doing parallel quicksort using
128 sorting threads + 80 uffd servicing threads). My sincere thanks to
Marty Mcfadden and Denis Plotnikov for the help along the way.
TODO
====
- hugetlbfs/shmem support
- performance
- more architectures
- cooperate with mprotect()-allowed processes (???)
- ...
References
==========
[1] https://lwn.net/Articles/666187/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git/log/?h=userfault
[3] https://github.com/denis-plotnikov/qemu/commits/background-snapshot-kvm
[4] https://github.com/LLNL/umap
[5] https://llnl-umap.readthedocs.io/en/develop/
[6] https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git/commit/?h=userfault&id=b245ecf6cf59156966f3da6e6b674f6695a5ffa5
[7] https://lkml.org/lkml/2018/11/21/370
[8] https://lkml.org/lkml/2018/12/30/64
This patch (of 19):
Add helper for writeprotect check. Will use it later.
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220163112.11409-2-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Commit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker")
changed the behavior when deflation happens automatically. Instead of
deflating when called by the OOM handler, the shrinker is used.
However, the balloon is not simply some other slab cache that should be
shrunk when under memory pressure. The shrinker does not have a concept
of priorities yet, so this behavior cannot be configured. Eventually once
that is in place, we might want to switch back after doing proper testing.
There was a report that this results in undesired side effects when
inflating the balloon to shrink the page cache. [1]
"When inflating the balloon against page cache (i.e. no free memory
remains) vmscan.c will both shrink page cache, but also invoke the
shrinkers -- including the balloon's shrinker. So the balloon
driver allocates memory which requires reclaim, vmscan gets this
memory by shrinking the balloon, and then the driver adds the
memory back to the balloon. Basically a busy no-op."
The name "deflate on OOM" makes it pretty clear when deflation should
happen - after other approaches to reclaim memory failed, not while
reclaiming. This allows to minimize the footprint of a guest - memory
will only be taken out of the balloon when really needed.
Keep using the shrinker for VIRTIO_BALLOON_F_FREE_PAGE_HINT, because
this has no such side effects. Always register the shrinker with
VIRTIO_BALLOON_F_FREE_PAGE_HINT now. We are always allowed to reuse free
pages that are still to be processed by the guest. The hypervisor takes
care of identifying and resolving possible races between processing a
hinting request and the guest reusing a page.
In contrast to pre commit 71994620bb25 ("virtio_balloon: replace oom
notifier with shrinker"), don't add a module parameter to configure the
number of pages to deflate on OOM. Can be re-added if really needed.
Also, pay attention that leak_balloon() returns the number of 4k pages -
convert it properly in virtio_balloon_oom_notify().
Testing done by Tyler for future reference:
Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42
GB file full of random bytes that we continually cat to /dev/null.
This fills the page cache as the file is read. Meanwhile, we trigger
the balloon to inflate, with a target size of 53 GB. This setup causes
the balloon inflation to pressure the page cache as the page cache is
also trying to grow. Afterwards we shrink the balloon back to zero (so
total deflate == total inflate).
Without this patch (kernel 4.19.0-5):
Inflation never reaches the target until we stop the "cat file >
/dev/null" process. Total inflation time was 542 seconds. The longest
period that made no net forward progress was 315 seconds.
Result of "grep balloon /proc/vmstat" after the test:
balloon_inflate 154828377
balloon_deflate 154828377
With this patch (kernel 5.6.0-rc4+):
Total inflation duration was 63 seconds. No deflate-queue activity
occurs when pressuring the page-cache.
Result of "grep balloon /proc/vmstat" after the test:
balloon_inflate 12968539
balloon_deflate 12968539
Conclusion: This patch fixes the issue. In the test it reduced
inflate/deflate activity by 12x, and reduced inflation time by 8.6x.
But more importantly, if we hadn't killed the "cat file > /dev/null"
process then, without the patch, the inflation process would never reach
the target.
[1] https://www.spinics.net/lists/linux-virtualization/msg40863.html
Link: http://lkml.kernel.org/r/20200311135523.18512-2-david@redhat.com
Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reported-by: Tyler Sanderson <tysand@google.com>
Tested-by: Tyler Sanderson <tysand@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add documentation for free page reporting. Currently the only consumer is
virtio-balloon, however it is possible that other drivers might make use
of this so it is best to add a bit of documetation explaining at a high
level how to use the API.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224730.29318.43815.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In order to keep ourselves from reporting pages that are just going to be
reused again in the case of heavy churn we can put a limit on how many
total pages we will process per pass. Doing this will allow the worker
thread to go into idle much more quickly so that we avoid competing with
other threads that might be allocating or freeing pages.
The logic added here will limit the worker thread to no more than one
sixteenth of the total free pages in a given area per list. Once that
limit is reached it will update the state so that at the end of the pass
we will reschedule the worker to try again in 2 seconds when the memory
churn has hopefully settled down.
Again this optimization doesn't show much of a benefit in the standard
case as the memory churn is minmal. However with page allocator shuffling
enabled the gain is quite noticeable. Below are the results with a THP
enabled version of the will-it-scale page_fault1 test showing the
improvement in iterations for 16 processes or threads.
Without:
tasks processes processes_idle threads threads_idle
16 8283274.75 0.17 5594261.00 38.15
With:
tasks processes processes_idle threads threads_idle
16 8767010.50 0.21 5791312.75 36.98
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224719.29318.72113.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Rather than walking over the same pages again and again to get to the
pages that have yet to be reported we can save ourselves a significant
amount of time by simply rotating the list so that when we have a full
list of reported pages the head of the list is pointing to the next
non-reported page. Doing this should save us some significant time when
processing each free list.
This doesn't gain us much in the standard case as all of the non-reported
pages should be near the top of the list already. However in the case of
page shuffling this results in a noticeable improvement. Below are the
will-it-scale page_fault1 w/ THP numbers for 16 tasks with and without
this patch.
Without:
tasks processes processes_idle threads threads_idle
16 8093776.25 0.17 5393242.00 38.20
With:
tasks processes processes_idle threads threads_idle
16 8283274.75 0.17 5594261.00 38.15
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224708.29318.16862.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add support for the page reporting feature provided by virtio-balloon.
Reporting differs from the regular balloon functionality in that is is
much less durable than a standard memory balloon. Instead of creating a
list of pages that cannot be accessed the pages are only inaccessible
while they are being indicated to the virtio interface. Once the
interface has acknowledged them they are placed back into their respective
free lists and are once again accessible by the guest system.
Unlike a standard balloon we don't inflate and deflate the pages. Instead
we perform the reporting, and once the reporting is completed it is
assumed that the page has been dropped from the guest and will be faulted
back in the next time the page is accessed.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224657.29318.68624.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Currently the page poisoning setting wasn't being enabled unless free page
hinting was enabled. However we will need the page poisoning tracking
logic as well for free page reporting. As such pull it out and make it a
separate bit of config in the probe function.
In addition we need to add support for the more recent init_on_free
feature which expects a behavior similar to page poisoning in that we
expect the page to be pre-zeroed.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224646.29318.695.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In order to pave the way for free page reporting in virtualized
environments we will need a way to get pages out of the free lists and
identify those pages after they have been returned. To accomplish this,
this patch adds the concept of a Reported Buddy, which is essentially
meant to just be the Uptodate flag used in conjunction with the Buddy page
type.
To prevent the reported pages from leaking outside of the buddy lists I
added a check to clear the PageReported bit in the del_page_from_free_list
function. As a result any reported page that is split, merged, or
allocated will have the flag cleared prior to the PageBuddy value being
cleared.
The process for reporting pages is fairly simple. Once we free a page
that meets the minimum order for page reporting we will schedule a worker
thread to start 2s or more in the future. That worker thread will begin
working from the lowest supported page reporting order up to MAX_ORDER - 1
pulling unreported pages from the free list and storing them in the
scatterlist.
When processing each individual free list it is necessary for the worker
thread to release the zone lock when it needs to stop and report the full
scatterlist of pages. To reduce the work of the next iteration the worker
thread will rotate the free list so that the first unreported page in the
free list becomes the first entry in the list.
It will then call a reporting function providing information on how many
entries are in the scatterlist. Once the function completes it will
return the pages to the free area from which they were allocated and start
over pulling more pages from the free areas until there are no longer
enough pages to report on to keep the worker busy, or we have processed as
many pages as were contained in the free area when we started processing
the list.
The worker thread will work in a round-robin fashion making its way though
each zone requesting reporting, and through each reportable free list
within that zone. Once all free areas within the zone have been processed
it will check to see if there have been any requests for reporting while
it was processing. If so it will reschedule the worker thread to start up
again in roughly 2s and exit.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224635.29318.19750.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
There are cases where we would benefit from avoiding having to go through
the allocation and free cycle to return an isolated page.
Examples for this might include page poisoning in which we isolate a page
and then put it back in the free list without ever having actually
allocated it.
This will enable us to also avoid notifiers for the future free page
reporting which will need to avoid retriggering page reporting when
returning pages that have been reported on.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224624.29318.89287.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In order to enable the use of the zone from the list manipulator functions
I will need access to the zone pointer. As it turns out most of the
accessors were always just being directly passed &zone->free_area[order]
anyway so it would make sense to just fold that into the function itself
and pass the zone and order as arguments instead of the free area.
In order to be able to reference the zone we need to move the declaration
of the functions down so that we have the zone defined before we define
the list manipulation functions. Since the functions are only used in the
file mm/page_alloc.c we can just move them there to reduce noise in the
header.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pankaj Gupta <pagupta@redhat.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224613.29318.43080.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "mm / virtio: Provide support for free page reporting", v17.
This series provides an asynchronous means of reporting free guest pages
to a hypervisor so that the memory associated with those pages can be
dropped and reused by other processes and/or guests on the host. Using
this it is possible to avoid unnecessary I/O to disk and greatly improve
performance in the case of memory overcommit on the host.
When enabled we will be performing a scan of free memory every 2 seconds
while pages of sufficiently high order are being freed. In each pass at
least one sixteenth of each free list will be reported. By doing this we
avoid racing against other threads that may be causing a high amount of
memory churn.
The lowest page order currently scanned when reporting pages is
pageblock_order so that this feature will not interfere with the use of
Transparent Huge Pages in the case of virtualization.
Currently this is only in use by virtio-balloon however there is the hope
that at some point in the future other hypervisors might be able to make
use of it. In the virtio-balloon/QEMU implementation the hypervisor is
currently using MADV_DONTNEED to indicate to the host kernel that the page
is currently free. It will be zeroed and faulted back into the guest the
next time the page is accessed.
To track if a page is reported or not the Uptodate flag was repurposed and
used as a Reported flag for Buddy pages. We walk though the free list
isolating pages and adding them to the scatterlist until we either
encounter the end of the list or have processed at least one sixteenth of
the pages that were listed in nr_free prior to us starting. If we fill
the scatterlist before we reach the end of the list we rotate the list so
that the first unreported page we encounter is moved to the head of the
list as that is where we will resume after we have freed the reported
pages back into the tail of the list.
Below are the results from various benchmarks. I primarily focused on two
tests. The first is the will-it-scale/page_fault2 test, and the other is
a modified version of will-it-scale/page_fault1 that was enabled to use
THP. I did this as it allows for better visibility into different parts
of the memory subsystem. The guest is running with 32G for RAM on one
node of a E5-2630 v3. The host has had some features such as CPU turbo
disabled in the BIOS.
Test page_fault1 (THP) page_fault2
Name tasks Process Iter STDEV Process Iter STDEV
Baseline 1 1012402.50 0.14% 361855.25 0.81%
16 8827457.25 0.09% 3282347.00 0.34%
Patches Applied 1 1007897.00 0.23% 361887.00 0.26%
16 8784741.75 0.39% 3240669.25 0.48%
Patches Enabled 1 1010227.50 0.39% 359749.25 0.56%
16 8756219.00 0.24% 3226608.75 0.97%
Patches Enabled 1 1050982.00 4.26% 357966.25 0.14%
page shuffle 16 8672601.25 0.49% 3223177.75 0.40%
Patches enabled 1 1003238.00 0.22% 360211.00 0.22%
shuffle w/ RFC 16 8767010.50 0.32% 3199874.00 0.71%
The results above are for a baseline with a linux-next-20191219 kernel,
that kernel with this patch set applied but page reporting disabled in
virtio-balloon, the patches applied and page reporting fully enabled, the
patches enabled with page shuffling enabled, and the patches applied with
page shuffling enabled and an RFC patch that makes used of MADV_FREE in
QEMU. These results include the deviation seen between the average value
reported here versus the high and/or low value. I observed that during
the test memory usage for the first three tests never dropped whereas with
the patches fully enabled the VM would drop to using only a few GB of the
host's memory when switching from memhog to page fault tests.
Any of the overhead visible with this patch set enabled seems due to page
faults caused by accessing the reported pages and the host zeroing the
page before giving it back to the guest. This overhead is much more
visible when using THP than with standard 4K pages. In addition page
shuffling seemed to increase the amount of faults generated due to an
increase in memory churn. The overehad is reduced when using MADV_FREE as
we can avoid the extra zeroing of the pages when they are reintroduced to
the host, as can be seen when the RFC is applied with shuffling enabled.
The overall guest size is kept fairly small to only a few GB while the
test is running. If the host memory were oversubscribed this patch set
should result in a performance improvement as swapping memory in the host
can be avoided.
A brief history on the background of free page reporting can be found at:
https://lore.kernel.org/lkml/29f43d5796feed0dec8e8bb98b187d9dac03b900.camel@linux.intel.com/
This patch (of 9):
Move the head/tail adding logic out of the shuffle code and into the
__free_one_page function since ultimately that is where it is really
needed anyway. By doing this we should be able to reduce the overhead and
can consolidate all of the list addition bits in one spot.
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: Pankaj Gupta <pagupta@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: wei qi <weiqi4@huawei.com>
Link: http://lkml.kernel.org/r/20200211224602.29318.84523.stgit@localhost.localdomain
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Some comments for MADV_FREE is revised and added to help people understand
the MADV_FREE code, especially the page flag, PG_swapbacked. This makes
page_is_file_cache() isn't consistent with its comments. So the function
is renamed to page_is_file_lru() to make them consistent again. All these
are put in one patch as one logical change.
Suggested-by: David Hildenbrand <david@redhat.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: David Rientjes <rientjes@google.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@surriel.com>
Link: http://lkml.kernel.org/r/20200317100342.2730705-1-ying.huang@intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This updates get_user_pages()'s argument in ksm_test_exit()'s comment
Signed-off-by: Li Chen <chenli@uniontech.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/30ac2417-f1c7-f337-0beb-df561295298c@uniontech.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Commit e496cf3d7821 ("thp: introduce CONFIG_TRANSPARENT_HUGE_PAGECACHE")
notes that it should be reverted when the PowerPC problem was fixed. The
commit fixing the PowerPC problem (953c66c2b22a) did not revert the
commit; instead setting CONFIG_TRANSPARENT_HUGE_PAGECACHE to the same as
CONFIG_TRANSPARENT_HUGEPAGE. Checking with Kirill and Aneesh, this was an
oversight, so remove the Kconfig symbol and undo the work of commit
e496cf3d7821.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Link: http://lkml.kernel.org/r/20200318140253.6141-6-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
If THP is disabled, find_subpage() can become a no-op by using
hpage_nr_pages() instead of compound_nr(). hpage_nr_pages() embeds a
check for PageTail, so we can drop the check here.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Link: http://lkml.kernel.org/r/20200318140253.6141-5-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The thp_fault_fallback and thp_file_fallback vmstats are incremented if
either the hugepage allocation fails through the page allocator or the
hugepage charge fails through mem cgroup.
This patch leaves this field untouched but adds two new fields,
thp_{fault,file}_fallback_charge, which is incremented only when the mem
cgroup charge fails.
This distinguishes between attempted hugepage allocations that fail due to
fragmentation (or low memory conditions) and those that fail due to mem
cgroup limits. That can be used to determine the impact of fragmentation
on the system by excluding faults that failed due to memcg usage.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Jeremy Cline <jcline@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061422070.7412@chino.kir.corp.google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The existing thp_fault_fallback indicates when thp attempts to allocate a
hugepage but fails, or if the hugepage cannot be charged to the mem cgroup
hierarchy.
Extend this to shmem as well. Adds a new thp_file_fallback to complement
thp_file_alloc that gets incremented when a hugepage is attempted to be
allocated but fails, or if it cannot be charged to the mem cgroup
hierarchy.
Additionally, remove the check for CONFIG_TRANSPARENT_HUGE_PAGECACHE from
shmem_alloc_hugepage() since it is only called with this configuration
option.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Jeremy Cline <jcline@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061421240.7412@chino.kir.corp.google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Currently the migration code doesn't migrate PG_readahead flag.
Theoretically this would incur slight performance loss as the application
might have to ramp its readahead back up again. Even though such problem
happens, it might be hidden by something else since migration is typically
triggered by compaction and NUMA balancing, any of which should be more
noticeable.
Migrate the flag after end_page_writeback() since it may clear PG_reclaim
flag, which is the same bit as PG_readahead, for the new page.
[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Link: http://lkml.kernel.org/r/1581640185-95731-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
It can currently happen that we store the status of a page twice:
* Once we detect that it is already on the target node
* Once we moved a bunch of pages, and a page that's already on the
target node is contained in the current interval.
Let's simplify the code and always call do_move_pages_to_node() in case we
did not queue a page for migration. Note that pages that are already on
the target node are not added to the pagelist and are, therefore, ignored
by do_move_pages_to_node() - there is no functional change.
The status of such a page is now only stored once.
[david@redhat.com rephrase changelog]
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/20200214003017.25558-5-richardw.yang@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
When pagelist is empty, it is not necessary to do the move and store.
Also it consolidate the empty list check in one place.
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/20200214003017.25558-4-richardw.yang@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
