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2018-02-18percpu: allow select gfp to be passed to underlying allocatorsDennis Zhou1-2/+2
The prior patch added support for passing gfp flags through to the underlying allocators. This patch allows users to pass along gfp flags (currently only __GFP_NORETRY and __GFP_NOWARN) to the underlying allocators. This should allow users to decide if they are ok with failing allocations recovering in a more graceful way. Additionally, gfp passing was done as additional flags in the previous patch. Instead, change this to caller passed semantics. GFP_KERNEL is also removed as the default flag. It continues to be used for internally caused underlying percpu allocations. V2: Removed gfp_percpu_mask in favor of doing it inline. Removed GFP_KERNEL as a default flag for __alloc_percpu_gfp. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2018-02-18percpu: add __GFP_NORETRY semantics to the percpu balancing pathDennis Zhou1-7/+11
Percpu memory using the vmalloc area based chunk allocator lazily populates chunks by first requesting the full virtual address space required for the chunk and subsequently adding pages as allocations come through. To ensure atomic allocations can succeed, a workqueue item is used to maintain a minimum number of empty pages. In certain scenarios, such as reported in [1], it is possible that physical memory becomes quite scarce which can result in either a rather long time spent trying to find free pages or worse, a kernel panic. This patch adds support for __GFP_NORETRY and __GFP_NOWARN passing them through to the underlying allocators. This should prevent any unnecessary panics potentially caused by the workqueue item. The passing of gfp around is as additional flags rather than a full set of flags. The next patch will change these to caller passed semantics. V2: Added const modifier to gfp flags in the balance path. Removed an extra whitespace. [1] https://lkml.org/lkml/2018/2/12/551 Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Reported-by: syzbot+adb03f3f0bb57ce3acda@syzkaller.appspotmail.com Acked-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2017-11-15mm: remove __GFP_COLDMel Gorman1-1/+1
As the page free path makes no distinction between cache hot and cold pages, there is no real useful ordering of pages in the free list that allocation requests can take advantage of. Juding from the users of __GFP_COLD, it is likely that a number of them are the result of copying other sites instead of actually measuring the impact. Remove the __GFP_COLD parameter which simplifies a number of paths in the page allocator. This is potentially controversial but bear in mind that the size of the per-cpu pagelists versus modern cache sizes means that the whole per-cpu list can often fit in the L3 cache. Hence, there is only a potential benefit for microbenchmarks that alloc/free pages in a tight loop. It's even worse when THP is taken into account which has little or no chance of getting a cache-hot page as the per-cpu list is bypassed and the zeroing of multiple pages will thrash the cache anyway. The truncate microbenchmarks are not shown as this patch affects the allocation path and not the free path. A page fault microbenchmark was tested but it showed no sigificant difference which is not surprising given that the __GFP_COLD branches are a miniscule percentage of the fault path. Link: http://lkml.kernel.org/r/20171018075952.10627-9-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-06-29percpu: fix static checker warnings in pcpu_destroy_chunkDennis Zhou1-1/+4
From 5021b97f4026334d2c8dfad80797dd1028cddd73 Mon Sep 17 00:00:00 2001 From: Dennis Zhou <dennisz@fb.com> Date: Thu, 29 Jun 2017 07:11:41 -0700 Add NULL check in pcpu_destroy_chunk to correct static checker warnings. Signed-off-by: Dennis Zhou <dennisz@fb.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2017-06-20percpu: add tracepoint support for percpu memoryDennis Zhou1-0/+2
Add support for tracepoints to the following events: chunk allocation, chunk free, area allocation, area free, and area allocation failure. This should let us replay percpu memory requests and evaluate corresponding decisions. Signed-off-by: Dennis Zhou <dennisz@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2017-06-20percpu: expose statistics about percpu memory via debugfsDennis Zhou1-0/+5
There is limited visibility into the use of percpu memory leaving us unable to reason about correctness of parameters and overall use of percpu memory. These counters and statistics aim to help understand basic statistics about percpu memory such as number of allocations over the lifetime, allocation sizes, and fragmentation. New Config: PERCPU_STATS Signed-off-by: Dennis Zhou <dennisz@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2017-03-06percpu: remove unused chunk_alloc parameter from pcpu_get_pages()Tahsin Erdogan1-4/+3
pcpu_get_pages() doesn't use chunk_alloc parameter, remove it. Fixes: fbbb7f4e149f ("percpu: remove the usage of separate populated bitmap in percpu-vm") Signed-off-by: Tahsin Erdogan <tahsin@google.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-09-02percpu: move region iterations out of pcpu_[de]populate_chunk()Tejun Heo1-41/+16
Previously, pcpu_[de]populate_chunk() were called with the range which may contain multiple target regions in it and pcpu_[de]populate_chunk() iterated over the regions. This has the benefit of batching up cache flushes for all the regions; however, we're planning to add more bookkeeping logic around [de]population to support atomic allocations and this delegation of iterations gets in the way. This patch moves the region iterations out of pcpu_[de]populate_chunk() into its callers - pcpu_alloc() and pcpu_reclaim() - so that we can later add logic to track more states around them. This change may make cache and tlb flushes more frequent but multi-region [de]populations are rare anyway and if this actually becomes a problem, it's not difficult to factor out cache flushes as separate callbacks which are directly invoked from percpu.c. Signed-off-by: Tejun Heo <tj@kernel.org>
2014-09-02percpu: move common parts out of pcpu_[de]populate_chunk()Tejun Heo1-26/+1
percpu-vm and percpu-km implement separate versions of pcpu_[de]populate_chunk() and some part which is or should be common are currently in the specific implementations. Make the following changes. * Allocate area clearing is moved from the pcpu_populate_chunk() implementations to pcpu_alloc(). This makes percpu-km's version noop. * Quick exit tests in pcpu_[de]populate_chunk() of percpu-vm are moved to their respective callers so that they are applied to percpu-km too. This doesn't make any meaningful difference as both functions are noop for percpu-km; however, this is more consistent and will help implementing atomic allocation support. Signed-off-by: Tejun Heo <tj@kernel.org>
2014-09-02percpu: remove @may_alloc from pcpu_get_pages()Tejun Heo1-7/+8
pcpu_get_pages() creates the temp pages array if not already allocated and returns the pointer to it. As the function is called from both [de]population paths and depopulation can only happen after at least one successful population, the param doesn't make any difference - the allocation will always happen on the population path anyway. Remove @may_alloc from pcpu_get_pages(). Also, add an lockdep assertion pcpu_alloc_mutex instead of vaguely stating that the exclusion is the caller's responsibility. Signed-off-by: Tejun Heo <tj@kernel.org>
2014-09-02percpu: remove the usage of separate populated bitmap in percpu-vmTejun Heo1-68/+25
percpu-vm uses pcpu_get_pages_and_bitmap() to acquire temp pages array and populated bitmap and uses the two during [de]population. The temp bitmap is used only to build the new bitmap that is copied to chunk->populated after the operation succeeds; however, the new bitmap can be trivially set after success without using the temp bitmap. This patch removes the temp populated bitmap usage from percpu-vm.c. * pcpu_get_pages_and_bitmap() is renamed to pcpu_get_pages() and no longer hands out the temp bitmap. * @populated arugment is dropped from all the related functions. @populated updates in pcpu_[un]map_pages() are dropped. * Two loops in pcpu_map_pages() are merged. * pcpu_[de]populated_chunk() modify chunk->populated bitmap directly from @page_start and @page_end after success. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Christoph Lameter <cl@linux.com>
2014-08-15percpu: perform tlb flush after pcpu_map_pages() failureTejun Heo1-0/+1
If pcpu_map_pages() fails midway, it unmaps the already mapped pages. Currently, it doesn't flush tlb after the partial unmapping. This may be okay in most cases as the established mapping hasn't been used at that point but it can go wrong and when it goes wrong it'd be extremely difficult to track down. Flush tlb after the partial unmapping. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
2014-08-15percpu: fix pcpu_alloc_pages() failure pathTejun Heo1-6/+15
When pcpu_alloc_pages() fails midway, pcpu_free_pages() is invoked to free what has already been allocated. The invocation is across the whole requested range and pcpu_free_pages() will try to free all non-NULL pages; unfortunately, this is incorrect as pcpu_get_pages_and_bitmap(), unlike what its comment suggests, doesn't clear the pages array and thus the array may have entries from the previous invocations making the partial failure path free incorrect pages. Fix it by open-coding the partial freeing of the already allocated pages. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
2012-06-20mm: fix kernel-doc warningsWanpeng Li1-1/+0
Fix kernel-doc warnings such as Warning(../mm/page_cgroup.c:432): No description found for parameter 'id' Warning(../mm/page_cgroup.c:432): Excess function parameter 'mem' description in 'swap_cgroup_record' Signed-off-by: Wanpeng Li <liwp@linux.vnet.ibm.com> Cc: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-20percpu: use bitmap_clearAkinobu Mita1-2/+1
Use bitmap_clear rather than clearing individual bits in a memory region. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Acked-by: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Tejun Heo <tj@kernel.org>
2011-11-22percpu: fix chunk range calculationTejun Heo1-6/+6
Percpu allocator recorded the cpus which map to the first and last units in pcpu_first/last_unit_cpu respectively and used them to determine the address range of a chunk - e.g. it assumed that the first unit has the lowest address in a chunk while the last unit has the highest address. This simply isn't true. Groups in a chunk can have arbitrary positive or negative offsets from the previous one and there is no guarantee that the first unit occupies the lowest offset while the last one the highest. Fix it by actually comparing unit offsets to determine cpus occupying the lowest and highest offsets. Also, rename pcu_first/last_unit_cpu to pcpu_low/high_unit_cpu to avoid confusion. The chunk address range is used to flush cache on vmalloc area map/unmap and decide whether a given address is in the first chunk by per_cpu_ptr_to_phys() and the bug was discovered by invalid per_cpu_ptr_to_phys() translation for crash_note. Kudos to Dave Young for tracking down the problem. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: WANG Cong <xiyou.wangcong@gmail.com> Reported-by: Dave Young <dyoung@redhat.com> Tested-by: Dave Young <dyoung@redhat.com> LKML-Reference: <4EC21F67.10905@redhat.com> Cc: stable @kernel.org
2011-11-22percpu: rename pcpu_mem_alloc to pcpu_mem_zallocBob Liu1-3/+2
Currently pcpu_mem_alloc() is implemented always return zeroed memory. So rename it to make user like pcpu_get_pages_and_bitmap() know don't reinit it. Signed-off-by: Bob Liu <lliubbo@gmail.com> Reviewed-by: Pekka Enberg <penberg@kernel.org> Reviewed-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org>
2011-01-13mm: remove gfp mask from pcpu_get_vm_areasDavid Rientjes1-1/+1
pcpu_get_vm_areas() only uses GFP_KERNEL allocations, so remove the gfp_t formal and use the mask internally. Signed-off-by: David Rientjes <rientjes@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-01percpu: move vmalloc based chunk management into percpu-vm.cTejun Heo1-0/+451
Separate out and move chunk management (creation/desctruction and [de]population) code into percpu-vm.c which is included by percpu.c and compiled together. The interface for chunk management is defined as follows. * pcpu_populate_chunk - populate the specified range of a chunk * pcpu_depopulate_chunk - depopulate the specified range of a chunk * pcpu_create_chunk - create a new chunk * pcpu_destroy_chunk - destroy a chunk, always preceded by full depop * pcpu_addr_to_page - translate address to physical address * pcpu_verify_alloc_info - check alloc_info is acceptable during init Other than wrapping vmalloc_to_page() inside pcpu_addr_to_page() and dummy pcpu_verify_alloc_info() implementation, this patch only moves code around. This separation is to allow alternate chunk management implementation. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Howells <dhowells@redhat.com> Cc: Graff Yang <graff.yang@gmail.com> Cc: Sonic Zhang <sonic.adi@gmail.com>