kernel.git/mm/swap.c, branch linux-3.12.y

mm/swap.c: flush lru pvecs on compound page arrival

2016-07-21T06:36:10Z

commit 8f182270dfec432e93fae14f9208a6b9af01009f upstream. Currently we can have compound pages held on per cpu pagevecs, which leads to a lot of memory unavailable for reclaim when needed. In the systems with hundreads of processors it can be GBs of memory. On of the way of reproducing the problem is to not call munmap explicitly on all mapped regions (i.e. after receiving SIGTERM). After that some pages (with THP enabled also huge pages) may end up on lru_add_pvec, example below. void main() { #pragma omp parallel { size_t size = 55 * 1000 * 1000; // smaller than MEM/CPUS void *p = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS , -1, 0); if (p != MAP_FAILED) memset(p, 0, size); //munmap(p, size); // uncomment to make the problem go away } } When we run it with THP enabled it will leave significant amount of memory on lru_add_pvec. This memory will be not reclaimed if we hit OOM, so when we run above program in a loop: for i in `seq 100`; do ./a.out; done many processes (95% in my case) will be killed by OOM. The primary point of the LRU add cache is to save the zone lru_lock contention with a hope that more pages will belong to the same zone and so their addition can be batched. The huge page is already a form of batched addition (it will add 512 worth of memory in one go) so skipping the batching seems like a safer option when compared to a potential excess in the caching which can be quite large and much harder to fix because lru_add_drain_all is way to expensive and it is not really clear what would be a good moment to call it. Similarly we can reproduce the problem on lru_deactivate_pvec by adding: madvise(p, size, MADV_FREE); after memset. This patch flushes lru pvecs on compound page arrival making the problem less severe - after applying it kill rate of above example drops to 0%, due to reducing maximum amount of memory held on pvec from 28MB (with THP) to 56kB per CPU. Suggested-by: Michal Hocko Link: http://lkml.kernel.org/r/1466180198-18854-1-git-send-email-lukasz.odzioba@intel.com Signed-off-by: Lukasz Odzioba Acked-by: Michal Hocko Cc: Kirill Shutemov Cc: Andrea Arcangeli Cc: Vladimir Davydov Cc: Ming Li Cc: Minchan Kim Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby

mm: pagemap: avoid unnecessary overhead when tracepoints are deactivated

2014-09-26T09:52:08Z

commit 24b7e5819ad5cbef2b7c7376510862aa8319d240 upstream. This was formerly the series "Improve sequential read throughput" which noted some major differences in performance of tiobench since 3.0. While there are a number of factors, two that dominated were the introduction of the fair zone allocation policy and changes to CFQ. The behaviour of fair zone allocation policy makes more sense than tiobench as a benchmark and CFQ defaults were not changed due to insufficient benchmarking. This series is what's left. It's one functional fix to the fair zone allocation policy when used on NUMA machines and a reduction of overhead in general. tiobench was used for the comparison despite its flaws as an IO benchmark as in this case we are primarily interested in the overhead of page allocator and page reclaim activity. On UMA, it makes little difference to overhead 3.16.0-rc3 3.16.0-rc3 vanilla lowercost-v5 User 383.61 386.77 System 403.83 401.74 Elapsed 5411.50 5413.11 On a 4-socket NUMA machine it's a bit more noticable 3.16.0-rc3 3.16.0-rc3 vanilla lowercost-v5 User 746.94 802.00 System 65336.22 40852.33 Elapsed 27553.52 27368.46 This patch (of 6): The LRU insertion and activate tracepoints take PFN as a parameter forcing the overhead to the caller. Move the overhead to the tracepoint fast-assign method to ensure the cost is only incurred when the tracepoint is active. Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm: non-atomically mark page accessed during page cache allocation where possible

2014-09-26T09:52:05Z

commit 2457aec63745e235bcafb7ef312b182d8682f0fc upstream. aops->write_begin may allocate a new page and make it visible only to have mark_page_accessed called almost immediately after. Once the page is visible the atomic operations are necessary which is noticable overhead when writing to an in-memory filesystem like tmpfs but should also be noticable with fast storage. The objective of the patch is to initialse the accessed information with non-atomic operations before the page is visible. The bulk of filesystems directly or indirectly use grab_cache_page_write_begin or find_or_create_page for the initial allocation of a page cache page. This patch adds an init_page_accessed() helper which behaves like the first call to mark_page_accessed() but may called before the page is visible and can be done non-atomically. The primary APIs of concern in this care are the following and are used by most filesystems. find_get_page find_lock_page find_or_create_page grab_cache_page_nowait grab_cache_page_write_begin All of them are very similar in detail to the patch creates a core helper pagecache_get_page() which takes a flags parameter that affects its behavior such as whether the page should be marked accessed or not. Then old API is preserved but is basically a thin wrapper around this core function. Each of the filesystems are then updated to avoid calling mark_page_accessed when it is known that the VM interfaces have already done the job. There is a slight snag in that the timing of the mark_page_accessed() has now changed so in rare cases it's possible a page gets to the end of the LRU as PageReferenced where as previously it might have been repromoted. This is expected to be rare but it's worth the filesystem people thinking about it in case they see a problem with the timing change. It is also the case that some filesystems may be marking pages accessed that previously did not but it makes sense that filesystems have consistent behaviour in this regard. The test case used to evaulate this is a simple dd of a large file done multiple times with the file deleted on each iterations. The size of the file is 1/10th physical memory to avoid dirty page balancing. In the async case it will be possible that the workload completes without even hitting the disk and will have variable results but highlight the impact of mark_page_accessed for async IO. The sync results are expected to be more stable. The exception is tmpfs where the normal case is for the "IO" to not hit the disk. The test machine was single socket and UMA to avoid any scheduling or NUMA artifacts. Throughput and wall times are presented for sync IO, only wall times are shown for async as the granularity reported by dd and the variability is unsuitable for comparison. As async results were variable do to writback timings, I'm only reporting the maximum figures. The sync results were stable enough to make the mean and stddev uninteresting. The performance results are reported based on a run with no profiling. Profile data is based on a separate run with oprofile running. async dd 3.15.0-rc3 3.15.0-rc3 vanilla accessed-v2 ext3 Max elapsed 13.9900 ( 0.00%) 11.5900 ( 17.16%) tmpfs Max elapsed 0.5100 ( 0.00%) 0.4900 ( 3.92%) btrfs Max elapsed 12.8100 ( 0.00%) 12.7800 ( 0.23%) ext4 Max elapsed 18.6000 ( 0.00%) 13.3400 ( 28.28%) xfs Max elapsed 12.5600 ( 0.00%) 2.0900 ( 83.36%) The XFS figure is a bit strange as it managed to avoid a worst case by sheer luck but the average figures looked reasonable. samples percentage ext3 86107 0.9783 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext3 23833 0.2710 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext3 5036 0.0573 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed ext4 64566 0.8961 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext4 5322 0.0713 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext4 2869 0.0384 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 62126 1.7675 vmlinux-3.15.0-rc4-vanilla mark_page_accessed xfs 1904 0.0554 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 103 0.0030 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed btrfs 10655 0.1338 vmlinux-3.15.0-rc4-vanilla mark_page_accessed btrfs 2020 0.0273 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed btrfs 587 0.0079 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed tmpfs 59562 3.2628 vmlinux-3.15.0-rc4-vanilla mark_page_accessed tmpfs 1210 0.0696 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed tmpfs 94 0.0054 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed [akpm@linux-foundation.org: don't run init_page_accessed() against an uninitialised pointer] Signed-off-by: Mel Gorman Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Rik van Riel Cc: Peter Zijlstra Tested-by: Prabhakar Lad Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm: do not use unnecessary atomic operations when adding pages to the LRU

2014-09-26T09:52:04Z

commit 6fb81a17d21f2a138b8f424af4cf379f2b694060 upstream. When adding pages to the LRU we clear the active bit unconditionally. As the page could be reachable from other paths we cannot use unlocked operations without risk of corruption such as a parallel mark_page_accessed. This patch tests if is necessary to clear the active flag before using an atomic operation. This potentially opens a tiny race when PageActive is checked as mark_page_accessed could be called after PageActive was checked. The race already exists but this patch changes it slightly. The consequence is that that the page may be promoted to the active list that might have been left on the inactive list before the patch. It's too tiny a race and too marginal a consequence to always use atomic operations for. Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Rik van Riel Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm: do not use atomic operations when releasing pages

2014-09-26T09:52:04Z

commit e3741b506c5088fa8c911bb5884c430f770fb49d upstream. There should be no references to it any more and a parallel mark should not be reordered against us. Use non-locked varient to clear page active. Signed-off-by: Mel Gorman Acked-by: Rik van Riel Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm: page_alloc: convert hot/cold parameter and immediate callers to bool

2014-09-26T09:52:03Z

commit b745bc85f21ea707e4ea1a91948055fa3e72c77b upstream. cold is a bool, make it one. Make the likely case the "if" part of the block instead of the else as according to the optimisation manual this is preferred. Signed-off-by: Mel Gorman Acked-by: Rik van Riel Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm/swap.c: clean up lru_cache_add functions

2014-09-26T09:52:02Z

commit 2329d3751b082b4fd354f334a88662d72abac52d upstream. In mm/swap.c, __lru_cache_add() is exported, but actually there are no users outside this file. This patch unexports __lru_cache_add(), and makes it static. It also exports lru_cache_add_file(), as it is use by cifs and fuse, which can loaded as modules. Signed-off-by: Jianyu Zhan Cc: Minchan Kim Cc: Johannes Weiner Cc: Shaohua Li Cc: Bob Liu Cc: Seth Jennings Cc: Joonsoo Kim Cc: Rafael Aquini Cc: Mel Gorman Acked-by: Rik van Riel Cc: Andrea Arcangeli Cc: Khalid Aziz Cc: Christoph Hellwig Reviewed-by: Zhang Yanfei Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm + fs: prepare for non-page entries in page cache radix trees

2014-09-26T09:51:58Z

commit 0cd6144aadd2afd19d1aca880153530c52957604 upstream. shmem mappings already contain exceptional entries where swap slot information is remembered. To be able to store eviction information for regular page cache, prepare every site dealing with the radix trees directly to handle entries other than pages. The common lookup functions will filter out non-page entries and return NULL for page cache holes, just as before. But provide a raw version of the API which returns non-page entries as well, and switch shmem over to use it. Signed-off-by: Johannes Weiner Reviewed-by: Rik van Riel Reviewed-by: Minchan Kim Cc: Andrea Arcangeli Cc: Bob Liu Cc: Christoph Hellwig Cc: Dave Chinner Cc: Greg Thelen Cc: Hugh Dickins Cc: Jan Kara Cc: KOSAKI Motohiro Cc: Luigi Semenzato Cc: Mel Gorman Cc: Metin Doslu Cc: Michel Lespinasse Cc: Ozgun Erdogan Cc: Peter Zijlstra Cc: Roman Gushchin Cc: Ryan Mallon Cc: Tejun Heo Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Jiri Slaby

mm: close PageTail race

2014-04-03T08:32:30Z

commit 668f9abbd4334e6c29fa8acd71635c4f9101caa7 upstream. Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned pages") introduces page_count(page) into memory compaction which dereferences page->first_page if PageTail(page). This results in a very rare NULL pointer dereference on the aforementioned page_count(page). Indeed, anything that does compound_head(), including page_count() is susceptible to racing with prep_compound_page() and seeing a NULL or dangling page->first_page pointer. This patch uses Andrea's implementation of compound_trans_head() that deals with such a race and makes it the default compound_head() implementation. This includes a read memory barrier that ensures that if PageTail(head) is true that we return a head page that is neither NULL nor dangling. The patch then adds a store memory barrier to prep_compound_page() to ensure page->first_page is set. This is the safest way to ensure we see the head page that we are expecting, PageTail(page) is already in the unlikely() path and the memory barriers are unfortunately required. Hugetlbfs is the exception, we don't enforce a store memory barrier during init since no race is possible. Signed-off-by: David Rientjes Cc: Holger Kiehl Cc: Christoph Lameter Cc: Rafael Aquini Cc: Vlastimil Babka Cc: Michal Hocko Cc: Mel Gorman Cc: Andrea Arcangeli Cc: Rik van Riel Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby

mm: hugetlbfs: fix hugetlbfs optimization

2014-02-06T19:22:14Z

commit 27c73ae759774e63313c1fbfeb17ba076cea64c5 upstream. Commit 7cb2ef56e6a8 ("mm: fix aio performance regression for database caused by THP") can cause dereference of a dangling pointer if split_huge_page runs during PageHuge() if there are updates to the tail_page->private field. Also it is repeating compound_head twice for hugetlbfs and it is running compound_head+compound_trans_head for THP when a single one is needed in both cases. The new code within the PageSlab() check doesn't need to verify that the THP page size is never bigger than the smallest hugetlbfs page size, to avoid memory corruption. A longstanding theoretical race condition was found while fixing the above (see the change right after the skip_unlock label, that is relevant for the compound_lock path too). By re-establishing the _mapcount tail refcounting for all compound pages, this also fixes the below problem: echo 0 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages BUG: Bad page state in process bash pfn:59a01 page:ffffea000139b038 count:0 mapcount:10 mapping: (null) index:0x0 page flags: 0x1c00000000008000(tail) Modules linked in: CPU: 6 PID: 2018 Comm: bash Not tainted 3.12.0+ #25 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: dump_stack+0x55/0x76 bad_page+0xd5/0x130 free_pages_prepare+0x213/0x280 __free_pages+0x36/0x80 update_and_free_page+0xc1/0xd0 free_pool_huge_page+0xc2/0xe0 set_max_huge_pages.part.58+0x14c/0x220 nr_hugepages_store_common.isra.60+0xd0/0xf0 nr_hugepages_store+0x13/0x20 kobj_attr_store+0xf/0x20 sysfs_write_file+0x189/0x1e0 vfs_write+0xc5/0x1f0 SyS_write+0x55/0xb0 system_call_fastpath+0x16/0x1b Signed-off-by: Khalid Aziz Signed-off-by: Andrea Arcangeli Tested-by: Khalid Aziz Cc: Pravin Shelar Cc: Greg Kroah-Hartman Cc: Ben Hutchings Cc: Christoph Lameter Cc: Johannes Weiner Cc: Mel Gorman Cc: Rik van Riel Cc: Andi Kleen Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Guillaume Morin Signed-off-by: Greg Kroah-Hartman