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authorDavid Rientjes <rientjes@google.com>2018-04-05 16:23:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-05 21:36:25 -0700
commita5c6d6509342785bef53bf9508e1842b303f1878 (patch)
treec741ae2db50b36dae555549172246676f9323f5f /Documentation
parent31286a8484a85e8b4e91ddb0f5415aee8a416827 (diff)
downloadlinux-a5c6d6509342785bef53bf9508e1842b303f1878.tar.bz2
mm, page_alloc: extend kernelcore and movablecore for percent
Both kernelcore= and movablecore= can be used to define the amount of ZONE_NORMAL and ZONE_MOVABLE on a system, respectively. This requires the system memory capacity to be known when specifying the command line, however. This introduces the ability to define both kernelcore= and movablecore= as a percentage of total system memory. This is convenient for systems software that wants to define the amount of ZONE_MOVABLE, for example, as a proportion of a system's memory rather than a hardcoded byte value. To define the percentage, the final character of the parameter should be a '%'. mhocko: "why is anyone using these options nowadays?" rientjes: : : Fragmentation of non-__GFP_MOVABLE pages due to low on memory : situations can pollute most pageblocks on the system, as much as 1GB of : slab being fragmented over 128GB of memory, for example. When the : amount of kernel memory is well bounded for certain systems, it is : better to aggressively reclaim from existing MIGRATE_UNMOVABLE : pageblocks rather than eagerly fallback to others. : : We have additional patches that help with this fragmentation if you're : interested, specifically kcompactd compaction of MIGRATE_UNMOVABLE : pageblocks triggered by fallback of non-__GFP_MOVABLE allocations and : draining of pcp lists back to the zone free area to prevent stranding. [rientjes@google.com: updates] Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1802131700160.71590@chino.kir.corp.google.com Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1802121622470.179479@chino.kir.corp.google.com Signed-off-by: David Rientjes <rientjes@google.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt54
1 files changed, 27 insertions, 27 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5ffe4c4121bd..7993021a1f6e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1840,30 +1840,29 @@
keepinitrd [HW,ARM]
kernelcore= [KNL,X86,IA-64,PPC]
- Format: nn[KMGTPE] | "mirror"
- This parameter
- specifies the amount of memory usable by the kernel
- for non-movable allocations. The requested amount is
- spread evenly throughout all nodes in the system. The
- remaining memory in each node is used for Movable
- pages. In the event, a node is too small to have both
- kernelcore and Movable pages, kernelcore pages will
- take priority and other nodes will have a larger number
- of Movable pages. The Movable zone is used for the
- allocation of pages that may be reclaimed or moved
- by the page migration subsystem. This means that
- HugeTLB pages may not be allocated from this zone.
- Note that allocations like PTEs-from-HighMem still
- use the HighMem zone if it exists, and the Normal
+ Format: nn[KMGTPE] | nn% | "mirror"
+ This parameter specifies the amount of memory usable by
+ the kernel for non-movable allocations. The requested
+ amount is spread evenly throughout all nodes in the
+ system as ZONE_NORMAL. The remaining memory is used for
+ movable memory in its own zone, ZONE_MOVABLE. In the
+ event, a node is too small to have both ZONE_NORMAL and
+ ZONE_MOVABLE, kernelcore memory will take priority and
+ other nodes will have a larger ZONE_MOVABLE.
+
+ ZONE_MOVABLE is used for the allocation of pages that
+ may be reclaimed or moved by the page migration
+ subsystem. Note that allocations like PTEs-from-HighMem
+ still use the HighMem zone if it exists, and the Normal
zone if it does not.
- Instead of specifying the amount of memory (nn[KMGTPE]),
- you can specify "mirror" option. In case "mirror"
+ It is possible to specify the exact amount of memory in
+ the form of "nn[KMGTPE]", a percentage of total system
+ memory in the form of "nn%", or "mirror". If "mirror"
option is specified, mirrored (reliable) memory is used
for non-movable allocations and remaining memory is used
- for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
- so you can NOT specify nn[KMGTPE] and "mirror" at the same
- time.
+ for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
+ are exclusive, so you cannot specify multiple forms.
kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
Format: <Controller#>[,poll interval]
@@ -2377,13 +2376,14 @@
mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
reporting absolute coordinates, such as tablets
- movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
- is similar to kernelcore except it specifies the
- amount of memory used for migratable allocations.
- If both kernelcore and movablecore is specified,
- then kernelcore will be at *least* the specified
- value but may be more. If movablecore on its own
- is specified, the administrator must be careful
+ movablecore= [KNL,X86,IA-64,PPC]
+ Format: nn[KMGTPE] | nn%
+ This parameter is the complement to kernelcore=, it
+ specifies the amount of memory used for migratable
+ allocations. If both kernelcore and movablecore is
+ specified, then kernelcore will be at *least* the
+ specified value but may be more. If movablecore on its
+ own is specified, the administrator must be careful
that the amount of memory usable for all allocations
is not too small.