user/sven/linux.git/mm/page_alloc.c, branch v4.12

mm: consider memblock reservations for deferred memory initialization sizing

2017-06-02T22:07:38Z

We have seen an early OOM killer invocation on ppc64 systems with crashkernel=4096M: kthreadd invoked oom-killer: gfp_mask=0x16040c0(GFP_KERNEL|__GFP_COMP|__GFP_NOTRACK), nodemask=7, order=0, oom_score_adj=0 kthreadd cpuset=/ mems_allowed=7 CPU: 0 PID: 2 Comm: kthreadd Not tainted 4.4.68-1.gd7fe927-default #1 Call Trace: dump_stack+0xb0/0xf0 (unreliable) dump_header+0xb0/0x258 out_of_memory+0x5f0/0x640 __alloc_pages_nodemask+0xa8c/0xc80 kmem_getpages+0x84/0x1a0 fallback_alloc+0x2a4/0x320 kmem_cache_alloc_node+0xc0/0x2e0 copy_process.isra.25+0x260/0x1b30 _do_fork+0x94/0x470 kernel_thread+0x48/0x60 kthreadd+0x264/0x330 ret_from_kernel_thread+0x5c/0xa4 Mem-Info: active_anon:0 inactive_anon:0 isolated_anon:0 active_file:0 inactive_file:0 isolated_file:0 unevictable:0 dirty:0 writeback:0 unstable:0 slab_reclaimable:5 slab_unreclaimable:73 mapped:0 shmem:0 pagetables:0 bounce:0 free:0 free_pcp:0 free_cma:0 Node 7 DMA free:0kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:52428800kB managed:110016kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:320kB slab_unreclaimable:4672kB kernel_stack:1152kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes lowmem_reserve[]: 0 0 0 0 Node 7 DMA: 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB = 0kB 0 total pagecache pages 0 pages in swap cache Swap cache stats: add 0, delete 0, find 0/0 Free swap = 0kB Total swap = 0kB 819200 pages RAM 0 pages HighMem/MovableOnly 817481 pages reserved 0 pages cma reserved 0 pages hwpoisoned the reason is that the managed memory is too low (only 110MB) while the rest of the the 50GB is still waiting for the deferred intialization to be done. update_defer_init estimates the initial memoty to initialize to 2GB at least but it doesn't consider any memory allocated in that range. In this particular case we've had Reserving 4096MB of memory at 128MB for crashkernel (System RAM: 51200MB) so the low 2GB is mostly depleted. Fix this by considering memblock allocations in the initial static initialization estimation. Move the max_initialise to reset_deferred_meminit and implement a simple memblock_reserved_memory helper which iterates all reserved blocks and sums the size of all that start below the given address. The cumulative size is than added on top of the initial estimation. This is still not ideal because reset_deferred_meminit doesn't consider holes and so reservation might be above the initial estimation whihch we ignore but let's make the logic simpler until we really need to handle more complicated cases. Fixes: 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set") Link: http://lkml.kernel.org/r/20170531104010.GI27783@dhcp22.suse.cz Signed-off-by: Michal Hocko Acked-by: Mel Gorman Tested-by: Srikar Dronamraju Cc: [4.2+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_alloc.c: make sure OOM victim can try allocations with no watermarks once

2017-06-02T22:07:37Z

Roman Gushchin has reported that the OOM killer can trivially selects next OOM victim when a thread doing memory allocation from page fault path was selected as first OOM victim. allocate invoked oom-killer: gfp_mask=0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null), order=0, oom_score_adj=0 allocate cpuset=/ mems_allowed=0 CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: oom_kill_process+0x219/0x3e0 out_of_memory+0x11d/0x480 __alloc_pages_slowpath+0xc84/0xd40 __alloc_pages_nodemask+0x245/0x260 alloc_pages_vma+0xa2/0x270 __handle_mm_fault+0xca9/0x10c0 handle_mm_fault+0xf3/0x210 __do_page_fault+0x240/0x4e0 trace_do_page_fault+0x37/0xe0 do_async_page_fault+0x19/0x70 async_page_fault+0x28/0x30 ... Out of memory: Kill process 492 (allocate) score 899 or sacrifice child Killed process 492 (allocate) total-vm:2052368kB, anon-rss:1894576kB, file-rss:4kB, shmem-rss:0kB allocate: page allocation failure: order:0, mode:0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null) allocate cpuset=/ mems_allowed=0 CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: __alloc_pages_slowpath+0xd32/0xd40 __alloc_pages_nodemask+0x245/0x260 alloc_pages_vma+0xa2/0x270 __handle_mm_fault+0xca9/0x10c0 handle_mm_fault+0xf3/0x210 __do_page_fault+0x240/0x4e0 trace_do_page_fault+0x37/0xe0 do_async_page_fault+0x19/0x70 async_page_fault+0x28/0x30 ... oom_reaper: reaped process 492 (allocate), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB ... allocate invoked oom-killer: gfp_mask=0x0(), nodemask=(null), order=0, oom_score_adj=0 allocate cpuset=/ mems_allowed=0 CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: oom_kill_process+0x219/0x3e0 out_of_memory+0x11d/0x480 pagefault_out_of_memory+0x68/0x80 mm_fault_error+0x8f/0x190 ? handle_mm_fault+0xf3/0x210 __do_page_fault+0x4b2/0x4e0 trace_do_page_fault+0x37/0xe0 do_async_page_fault+0x19/0x70 async_page_fault+0x28/0x30 ... Out of memory: Kill process 233 (firewalld) score 10 or sacrifice child Killed process 233 (firewalld) total-vm:246076kB, anon-rss:20956kB, file-rss:0kB, shmem-rss:0kB There is a race window that the OOM reaper completes reclaiming the first victim's memory while nothing but mutex_trylock() prevents the first victim from calling out_of_memory() from pagefault_out_of_memory() after memory allocation for page fault path failed due to being selected as an OOM victim. This is a side effect of commit 9a67f6488eca926f ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath") because that commit silently changed the behavior from /* Avoid allocations with no watermarks from looping endlessly */ to /* * Give up allocations without trying memory reserves if selected * as an OOM victim */ in __alloc_pages_slowpath() by moving the location to check TIF_MEMDIE flag. I have noticed this change but I didn't post a patch because I thought it is an acceptable change other than noise by warn_alloc() because !__GFP_NOFAIL allocations are allowed to fail. But we overlooked that failing memory allocation from page fault path makes difference due to the race window explained above. While it might be possible to add a check to pagefault_out_of_memory() that prevents the first victim from calling out_of_memory() or remove out_of_memory() from pagefault_out_of_memory(), changing pagefault_out_of_memory() does not suppress noise by warn_alloc() when allocating thread was selected as an OOM victim. There is little point with printing similar backtraces and memory information from both out_of_memory() and warn_alloc(). Instead, if we guarantee that current thread can try allocations with no watermarks once when current thread looping inside __alloc_pages_slowpath() was selected as an OOM victim, we can follow "who can use memory reserves" rules and suppress noise by warn_alloc() and prevent memory allocations from page fault path from calling pagefault_out_of_memory(). If we take the comment literally, this patch would do - if (test_thread_flag(TIF_MEMDIE)) - goto nopage; + if (alloc_flags == ALLOC_NO_WATERMARKS || (gfp_mask & __GFP_NOMEMALLOC)) + goto nopage; because gfp_pfmemalloc_allowed() returns false if __GFP_NOMEMALLOC is given. But if I recall correctly (I couldn't find the message), the condition is meant to apply to only OOM victims despite the comment. Therefore, this patch preserves TIF_MEMDIE check. Fixes: 9a67f6488eca926f ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath") Link: http://lkml.kernel.org/r/201705192112.IAF69238.OQOHSJLFOFFMtV@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Reported-by: Roman Gushchin Tested-by: Roman Gushchin Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: [4.11] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: introduce memalloc_noreclaim_{save,restore}

2017-05-09T00:15:15Z

The previous patch ("mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC") has shown that simply setting and clearing PF_MEMALLOC in current->flags can result in wrongly clearing a pre-existing PF_MEMALLOC flag and potentially lead to recursive reclaim. Let's introduce helpers that support proper nesting by saving the previous stat of the flag, similar to the existing memalloc_noio_* and memalloc_nofs_* helpers. Convert existing setting/clearing of PF_MEMALLOC within mm to the new helpers. There are no known issues with the converted code, but the change makes it more robust. Link: http://lkml.kernel.org/r/20170405074700.29871-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Suggested-by: Michal Hocko Acked-by: Michal Hocko Acked-by: Hillf Danton Cc: Mel Gorman Cc: Johannes Weiner Cc: Andrey Ryabinin Cc: Boris Brezillon Cc: Chris Leech Cc: "David S. Miller" Cc: Eric Dumazet Cc: Josef Bacik Cc: Lee Duncan Cc: Michal Hocko Cc: Richard Weinberger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC

2017-05-09T00:15:15Z

Patch series "more robust PF_MEMALLOC handling" This series aims to unify the setting and clearing of PF_MEMALLOC, which prevents recursive reclaim. There are some places that clear the flag unconditionally from current->flags, which may result in clearing a pre-existing flag. This already resulted in a bug report that Patch 1 fixes (without the new helpers, to make backporting easier). Patch 2 introduces the new helpers, modelled after existing memalloc_noio_* and memalloc_nofs_* helpers, and converts mm core to use them. Patches 3 and 4 convert non-mm code. This patch (of 4): __alloc_pages_direct_compact() sets PF_MEMALLOC to prevent deadlock during page migration by lock_page() (see the comment in __unmap_and_move()). Then it unconditionally clears the flag, which can clear a pre-existing PF_MEMALLOC flag and result in recursive reclaim. This was not a problem until commit a8161d1ed609 ("mm, page_alloc: restructure direct compaction handling in slowpath"), because direct compation was called only after direct reclaim, which was skipped when PF_MEMALLOC flag was set. Even now it's only a theoretical issue, as the new callsite of __alloc_pages_direct_compact() is reached only for costly orders and when gfp_pfmemalloc_allowed() is true, which means either __GFP_NOMEMALLOC is in gfp_flags or in_interrupt() is true. There is no such known context, but let's play it safe and make __alloc_pages_direct_compact() robust for cases where PF_MEMALLOC is already set. Fixes: a8161d1ed609 ("mm, page_alloc: restructure direct compaction handling in slowpath") Link: http://lkml.kernel.org/r/20170405074700.29871-2-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reported-by: Andrey Ryabinin Acked-by: Michal Hocko Acked-by: Hillf Danton Cc: Mel Gorman Cc: Johannes Weiner Cc: Boris Brezillon Cc: Chris Leech Cc: "David S. Miller" Cc: Eric Dumazet Cc: Josef Bacik Cc: Lee Duncan Cc: Michal Hocko Cc: Richard Weinberger Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: restrict async compaction to pageblocks of same migratetype

2017-05-09T00:15:10Z

The migrate scanner in async compaction is currently limited to MIGRATE_MOVABLE pageblocks. This is a heuristic intended to reduce latency, based on the assumption that non-MOVABLE pageblocks are unlikely to contain movable pages. However, with the exception of THP's, most high-order allocations are not movable. Should the async compaction succeed, this increases the chance that the non-MOVABLE allocations will fallback to a MOVABLE pageblock, making the long-term fragmentation worse. This patch attempts to help the situation by changing async direct compaction so that the migrate scanner only scans the pageblocks of the requested migratetype. If it's a non-MOVABLE type and there are such pageblocks that do contain movable pages, chances are that the allocation can succeed within one of such pageblocks, removing the need for a fallback. If that fails, the subsequent sync attempt will ignore this restriction. In testing based on 4.9 kernel with stress-highalloc from mmtests configured for order-4 GFP_KERNEL allocations, this patch has reduced the number of unmovable allocations falling back to movable pageblocks by 30%. The number of movable allocations falling back is reduced by 12%. Link: http://lkml.kernel.org/r/20170307131545.28577-8-vbabka@suse.cz Signed-off-by: Vlastimil Babka Cc: Mel Gorman Cc: Johannes Weiner Cc: Joonsoo Kim Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, page_alloc: count movable pages when stealing from pageblock

2017-05-09T00:15:10Z

When stealing pages from pageblock of a different migratetype, we count how many free pages were stolen, and change the pageblock's migratetype if more than half of the pageblock was free. This might be too conservative, as there might be other pages that are not free, but were allocated with the same migratetype as our allocation requested. While we cannot determine the migratetype of allocated pages precisely (at least without the page_owner functionality enabled), we can count pages that compaction would try to isolate for migration - those are either on LRU or __PageMovable(). The rest can be assumed to be MIGRATE_RECLAIMABLE or MIGRATE_UNMOVABLE, which we cannot easily distinguish. This counting can be done as part of free page stealing with little additional overhead. The page stealing code is changed so that it considers free pages plus pages of the "good" migratetype for the decision whether to change pageblock's migratetype. The result should be more accurate migratetype of pageblocks wrt the actual pages in the pageblocks, when stealing from semi-occupied pageblocks. This should help the efficiency of page grouping by mobility. In testing based on 4.9 kernel with stress-highalloc from mmtests configured for order-4 GFP_KERNEL allocations, this patch has reduced the number of unmovable allocations falling back to movable pageblocks by 47%. The number of movable allocations falling back to other pageblocks are increased by 55%, but these events don't cause permanent fragmentation, so the tradeoff should be positive. Later patches also offset the movable fallback increase to some extent. [akpm@linux-foundation.org: merge fix] Link: http://lkml.kernel.org/r/20170307131545.28577-5-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman Cc: Johannes Weiner Cc: Joonsoo Kim Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, page_alloc: split smallest stolen page in fallback

2017-05-09T00:15:09Z

The __rmqueue_fallback() function is called when there's no free page of requested migratetype, and we need to steal from a different one. There are various heuristics to make this event infrequent and reduce permanent fragmentation. The main one is to try stealing from a pageblock that has the most free pages, and possibly steal them all at once and convert the whole pageblock. Precise searching for such pageblock would be expensive, so instead the heuristics walks the free lists from MAX_ORDER down to requested order and assumes that the block with highest-order free page is likely to also have the most free pages in total. Chances are that together with the highest-order page, we steal also pages of lower orders from the same block. But then we still split the highest order page. This is wasteful and can contribute to fragmentation instead of avoiding it. This patch thus changes __rmqueue_fallback() to just steal the page(s) and put them on the freelist of the requested migratetype, and only report whether it was successful. Then we pick (and eventually split) the smallest page with __rmqueue_smallest(). This all happens under zone lock, so nobody can steal it from us in the process. This should reduce fragmentation due to fallbacks. At worst we are only stealing a single highest-order page and waste some cycles by moving it between lists and then removing it, but fallback is not exactly hot path so that should not be a concern. As a side benefit the patch removes some duplicate code by reusing __rmqueue_smallest(). [vbabka@suse.cz: fix endless loop in the modified __rmqueue()] Link: http://lkml.kernel.org/r/59d71b35-d556-4fc9-ee2e-1574259282fd@suse.cz Link: http://lkml.kernel.org/r/20170307131545.28577-4-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman Acked-by: Johannes Weiner Cc: Joonsoo Kim Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'trace-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2017-05-04T01:41:21Z

Pull tracing updates from Steven Rostedt: "New features for this release: - Pretty much a full rewrite of the processing of function plugins. i.e. echo do_IRQ:stacktrace > set_ftrace_filter - The rewrite was needed to add plugins to be unique to tracing instances. i.e. mkdir instance/foo; cd instances/foo; echo do_IRQ:stacktrace > set_ftrace_filter The old way was written very hacky. This removes a lot of those hacks. - New "function-fork" tracing option. When set, pids in the set_ftrace_pid will have their children added when the processes with their pids listed in the set_ftrace_pid file forks. - Exposure of "maxactive" for kretprobe in kprobe_events - Allow for builtin init functions to be traced by the function tracer (via the kernel command line). Module init function tracing will come in the next release. - Added more selftests, and have selftests also test in an instance" * tag 'trace-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (60 commits) ring-buffer: Return reader page back into existing ring buffer selftests: ftrace: Allow some event trigger tests to run in an instance selftests: ftrace: Have some basic tests run in a tracing instance too selftests: ftrace: Have event tests also run in an tracing instance selftests: ftrace: Make func_event_triggers and func_traceonoff_triggers tests do instances selftests: ftrace: Allow some tests to be run in a tracing instance tracing/ftrace: Allow for instances to trigger their own stacktrace probes tracing/ftrace: Allow for the traceonoff probe be unique to instances tracing/ftrace: Enable snapshot function trigger to work with instances tracing/ftrace: Allow instances to have their own function probes tracing/ftrace: Add a better way to pass data via the probe functions ftrace: Dynamically create the probe ftrace_ops for the trace_array tracing: Pass the trace_array into ftrace_probe_ops functions tracing: Have the trace_array hold the list of registered func probes ftrace: If the hash for a probe fails to update then free what was initialized ftrace: Have the function probes call their own function ftrace: Have each function probe use its own ftrace_ops ftrace: Have unregister_ftrace_function_probe_func() return a value ftrace: Add helper function ftrace_hash_move_and_update_ops() ftrace: Remove data field from ftrace_func_probe structure ...

mm, page_alloc: remove debug_guardpage_minorder() test in warn_alloc()

2017-05-03T22:52:11Z

Commit c0a32fc5a2e4 ("mm: more intensive memory corruption debugging") changed to check debug_guardpage_minorder() > 0 when reporting allocation failures. The reasoning was When we use guard page to debug memory corruption, it shrinks available pages to 1/2, 1/4, 1/8 and so on, depending on parameter value. In such case memory allocation failures can be common and printing errors can flood dmesg. If somebody debug corruption, allocation failures are not the things he/she is interested about. but this is misguided. Allocation requests with __GFP_NOWARN flag by definition do not cause flooding of allocation failure messages. Allocation requests with __GFP_NORETRY flag likely also have __GFP_NOWARN flag. Costly allocation requests likely also have __GFP_NOWARN flag. Allocation requests without __GFP_DIRECT_RECLAIM flag likely also have __GFP_NOWARN flag or __GFP_HIGH flag. Non-costly allocation requests with __GFP_DIRECT_RECLAIM flag basically retry forever due to the "too small to fail" memory-allocation rule. Therefore, as a whole, shrinking available pages by debug_guardpage_minorder= kernel boot parameter might cause flooding of OOM killer messages but unlikely causes flooding of allocation failure messages. Let's remove debug_guardpage_minorder() > 0 check which would likely be pointless. Link: http://lkml.kernel.org/r/1491910035-4231-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Cc: Stanislaw Gruszka Cc: Mel Gorman Cc: Andrea Arcangeli Cc: "Rafael J . Wysocki" Cc: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: enable page poisoning early at boot

2017-05-03T22:52:10Z

On SPARSEMEM systems page poisoning is enabled after buddy is up, because of the dependency on page extension init. This causes the pages released by free_all_bootmem not to be poisoned. This either delays or misses the identification of some issues because the pages have to undergo another cycle of alloc-free-alloc for any corruption to be detected. Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON flag. Since all the free pages will now be poisoned, the flag need not be verified before checking the poison during an alloc. [vinmenon@codeaurora.org: fix Kconfig] Link: http://lkml.kernel.org/r/1490878002-14423-1-git-send-email-vinmenon@codeaurora.org Link: http://lkml.kernel.org/r/1490358246-11001-1-git-send-email-vinmenon@codeaurora.org Signed-off-by: Vinayak Menon Acked-by: Laura Abbott Tested-by: Laura Abbott Cc: Joonsoo Kim Cc: Michal Hocko Cc: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds