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2014-06-04mm, compaction: properly signal and act upon lock and need_sched() contentionVlastimil Babka
Compaction uses compact_checklock_irqsave() function to periodically check for lock contention and need_resched() to either abort async compaction, or to free the lock, schedule and retake the lock. When aborting, cc->contended is set to signal the contended state to the caller. Two problems have been identified in this mechanism. First, compaction also calls directly cond_resched() in both scanners when no lock is yet taken. This call either does not abort async compaction, or set cc->contended appropriately. This patch introduces a new compact_should_abort() function to achieve both. In isolate_freepages(), the check frequency is reduced to once by SWAP_CLUSTER_MAX pageblocks to match what the migration scanner does in the preliminary page checks. In case a pageblock is found suitable for calling isolate_freepages_block(), the checks within there are done on higher frequency. Second, isolate_freepages() does not check if isolate_freepages_block() aborted due to contention, and advances to the next pageblock. This violates the principle of aborting on contention, and might result in pageblocks not being scanned completely, since the scanning cursor is advanced. This problem has been noticed in the code by Joonsoo Kim when reviewing related patches. This patch makes isolate_freepages_block() check the cc->contended flag and abort. In case isolate_freepages() has already isolated some pages before aborting due to contention, page migration will proceed, which is OK since we do not want to waste the work that has been done, and page migration has own checks for contention. However, we do not want another isolation attempt by either of the scanners, so cc->contended flag check is added also to compaction_alloc() and compact_finished() to make sure compaction is aborted right after the migration. The outcome of the patch should be reduced lock contention by async compaction and lower latencies for higher-order allocations where direct compaction is involved. [akpm@linux-foundation.org: fix typo in comment] Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Tested-by: Shawn Guo <shawn.guo@linaro.org> Tested-by: Kevin Hilman <khilman@linaro.org> Tested-by: Stephen Warren <swarren@nvidia.com> Tested-by: Fabio Estevam <fabio.estevam@freescale.com> Cc: David Rientjes <rientjes@google.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm/compaction: avoid rescanning pageblocks in isolate_freepagesVlastimil Babka
The compaction free scanner in isolate_freepages() currently remembers PFN of the highest pageblock where it successfully isolates, to be used as the starting pageblock for the next invocation. The rationale behind this is that page migration might return free pages to the allocator when migration fails and we don't want to skip them if the compaction continues. Since migration now returns free pages back to compaction code where they can be reused, this is no longer a concern. This patch changes isolate_freepages() so that the PFN for restarting is updated with each pageblock where isolation is attempted. Using stress-highalloc from mmtests, this resulted in 10% reduction of the pages scanned by the free scanner. Note that the somewhat similar functionality that records highest successful pageblock in zone->compact_cached_free_pfn, remains unchanged. This cache is used when the whole compaction is restarted, not for multiple invocations of the free scanner during single compaction. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm/compaction: do not count migratepages when unnecessaryVlastimil Babka
During compaction, update_nr_listpages() has been used to count remaining non-migrated and free pages after a call to migrage_pages(). The freepages counting has become unneccessary, and it turns out that migratepages counting is also unnecessary in most cases. The only situation when it's needed to count cc->migratepages is when migrate_pages() returns with a negative error code. Otherwise, the non-negative return value is the number of pages that were not migrated, which is exactly the count of remaining pages in the cc->migratepages list. Furthermore, any non-zero count is only interesting for the tracepoint of mm_compaction_migratepages events, because after that all remaining unmigrated pages are put back and their count is set to 0. This patch therefore removes update_nr_listpages() completely, and changes the tracepoint definition so that the manual counting is done only when the tracepoint is enabled, and only when migrate_pages() returns a negative error code. Furthermore, migrate_pages() and the tracepoints won't be called when there's nothing to migrate. This potentially avoids some wasted cycles and reduces the volume of uninteresting mm_compaction_migratepages events where "nr_migrated=0 nr_failed=0". In the stress-highalloc mmtest, this was about 75% of the events. The mm_compaction_isolate_migratepages event is better for determining that nothing was isolated for migration, and this one was just duplicating the info. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm, compaction: terminate async compaction when reschedulingDavid Rientjes
Async compaction terminates prematurely when need_resched(), see compact_checklock_irqsave(). This can never trigger, however, if the cond_resched() in isolate_migratepages_range() always takes care of the scheduling. If the cond_resched() actually triggers, then terminate this pageblock scan for async compaction as well. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm, compaction: embed migration mode in compact_controlDavid Rientjes
We're going to want to manipulate the migration mode for compaction in the page allocator, and currently compact_control's sync field is only a bool. Currently, we only do MIGRATE_ASYNC or MIGRATE_SYNC_LIGHT compaction depending on the value of this bool. Convert the bool to enum migrate_mode and pass the migration mode in directly. Later, we'll want to avoid MIGRATE_SYNC_LIGHT for thp allocations in the pagefault patch to avoid unnecessary latency. This also alters compaction triggered from sysfs, either for the entire system or for a node, to force MIGRATE_SYNC. [akpm@linux-foundation.org: fix build] [iamjoonsoo.kim@lge.com: use MIGRATE_SYNC in alloc_contig_range()] Signed-off-by: David Rientjes <rientjes@google.com> Suggested-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm, compaction: add per-zone migration pfn cache for async compactionDavid Rientjes
Each zone has a cached migration scanner pfn for memory compaction so that subsequent calls to memory compaction can start where the previous call left off. Currently, the compaction migration scanner only updates the per-zone cached pfn when pageblocks were not skipped for async compaction. This creates a dependency on calling sync compaction to avoid having subsequent calls to async compaction from scanning an enormous amount of non-MOVABLE pageblocks each time it is called. On large machines, this could be potentially very expensive. This patch adds a per-zone cached migration scanner pfn only for async compaction. It is updated everytime a pageblock has been scanned in its entirety and when no pages from it were successfully isolated. The cached migration scanner pfn for sync compaction is updated only when called for sync compaction. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Greg Thelen <gthelen@google.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm, compaction: return failed migration target pages back to freelistDavid Rientjes
Greg reported that he found isolated free pages were returned back to the VM rather than the compaction freelist. This will cause holes behind the free scanner and cause it to reallocate additional memory if necessary later. He detected the problem at runtime seeing that ext4 metadata pages (esp the ones read by "sbi->s_group_desc[i] = sb_bread(sb, block)") were constantly visited by compaction calls of migrate_pages(). These pages had a non-zero b_count which caused fallback_migrate_page() -> try_to_release_page() -> try_to_free_buffers() to fail. Memory compaction works by having a "freeing scanner" scan from one end of a zone which isolates pages as migration targets while another "migrating scanner" scans from the other end of the same zone which isolates pages for migration. When page migration fails for an isolated page, the target page is returned to the system rather than the freelist built by the freeing scanner. This may require the freeing scanner to continue scanning memory after suitable migration targets have already been returned to the system needlessly. This patch returns destination pages to the freeing scanner freelist when page migration fails. This prevents unnecessary work done by the freeing scanner but also encourages memory to be as compacted as possible at the end of the zone. Signed-off-by: David Rientjes <rientjes@google.com> Reported-by: Greg Thelen <gthelen@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm, migration: add destination page freeing callbackDavid Rientjes
Memory migration uses a callback defined by the caller to determine how to allocate destination pages. When migration fails for a source page, however, it frees the destination page back to the system. This patch adds a memory migration callback defined by the caller to determine how to free destination pages. If a caller, such as memory compaction, builds its own freelist for migration targets, this can reuse already freed memory instead of scanning additional memory. If the caller provides a function to handle freeing of destination pages, it is called when page migration fails. If the caller passes NULL then freeing back to the system will be handled as usual. This patch introduces no functional change. Signed-off-by: David Rientjes <rientjes@google.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Greg Thelen <gthelen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm/compaction: cleanup isolate_freepages()Vlastimil Babka
isolate_freepages() is currently somewhat hard to follow thanks to many looks like it is related to the 'low_pfn' variable, but in fact it is not. This patch renames the 'high_pfn' variable to a hopefully less confusing name, and slightly changes its handling without a functional change. A comment made obsolete by recent changes is also updated. [akpm@linux-foundation.org: comment fixes, per Minchan] [iamjoonsoo.kim@lge.com: cleanups] Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Cc: Dongjun Shin <d.j.shin@samsung.com> Cc: Sunghwan Yun <sunghwan.yun@samsung.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04mm/compaction: clean up unused code linesHeesub Shin
Remove code lines currently not in use or never called. Signed-off-by: Heesub Shin <heesub.shin@samsung.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Dongjun Shin <d.j.shin@samsung.com> Cc: Sunghwan Yun <sunghwan.yun@samsung.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Cc: Dongjun Shin <d.j.shin@samsung.com> Cc: Sunghwan Yun <sunghwan.yun@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-05-06mm/compaction: make isolate_freepages start at pageblock boundaryVlastimil Babka
The compaction freepage scanner implementation in isolate_freepages() starts by taking the current cc->free_pfn value as the first pfn. In a for loop, it scans from this first pfn to the end of the pageblock, and then subtracts pageblock_nr_pages from the first pfn to obtain the first pfn for the next for loop iteration. This means that when cc->free_pfn starts at offset X rather than being aligned on pageblock boundary, the scanner will start at offset X in all scanned pageblock, ignoring potentially many free pages. Currently this can happen when a) zone's end pfn is not pageblock aligned, or b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE enabled and a hole spanning the beginning of a pageblock This patch fixes the problem by aligning the initial pfn in isolate_freepages() to pageblock boundary. This also permits replacing the end-of-pageblock alignment within the for loop with a simple pageblock_nr_pages increment. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: Heesub Shin <heesub.shin@samsung.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Dongjun Shin <d.j.shin@samsung.com> Cc: Sunghwan Yun <sunghwan.yun@samsung.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm, compaction: determine isolation mode only onceDavid Rientjes
The conditions that control the isolation mode in isolate_migratepages_range() do not change during the iteration, so extract them out and only define the value once. This actually does have an effect, gcc doesn't optimize it itself because of cc->sync. Signed-off-by: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm/compaction: clean-up code on success of ballon isolationJoonsoo Kim
It is just for clean-up to reduce code size and improve readability. There is no functional change. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm/compaction: check pageblock suitability once per pageblockJoonsoo Kim
isolation_suitable() and migrate_async_suitable() is used to be sure that this pageblock range is fine to be migragted. It isn't needed to call it on every page. Current code do well if not suitable, but, don't do well when suitable. 1) It re-checks isolation_suitable() on each page of a pageblock that was already estabilished as suitable. 2) It re-checks migrate_async_suitable() on each page of a pageblock that was not entered through the next_pageblock: label, because last_pageblock_nr is not otherwise updated. This patch fixes situation by 1) calling isolation_suitable() only once per pageblock and 2) always updating last_pageblock_nr to the pageblock that was just checked. Additionally, move PageBuddy() check after pageblock unit check, since pageblock check is the first thing we should do and makes things more simple. [vbabka@suse.cz: rephrase commit description] Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm/compaction: change the timing to check to drop the spinlockJoonsoo Kim
It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn page. This may results in below situation while isolating migratepage. 1. try isolate 0x0 ~ 0x200 pfn pages. 2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop the spinlock. 3. Then, to complete isolating, retry to aquire the lock. I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the criteria about dropping the lock. This has no harm 0x0 pfn, because, at this time, locked variable would be false. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm/compaction: do not call suitable_migration_target() on every pageJoonsoo Kim
suitable_migration_target() checks that pageblock is suitable for migration target. In isolate_freepages_block(), it is called on every page and this is inefficient. So make it called once per pageblock. suitable_migration_target() also checks if page is highorder or not, but it's criteria for highorder is pageblock order. So calling it once within pageblock range has no problem. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07mm/compaction: disallow high-order page for migration targetJoonsoo Kim
Purpose of compaction is to get a high order page. Currently, if we find high-order page while searching migration target page, we break it to order-0 pages and use them as migration target. It is contrary to purpose of compaction, so disallow high-order page to be used for migration target. Additionally, clean-up logic in suitable_migration_target() to simplify the code. There is no functional changes from this clean-up. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-03mm/compaction.c: mark function as staticRashika Kheria
Mark function as static in compaction.c because it is not used outside this file. This eliminates the following warning from mm/compaction.c: mm/compaction.c:1190:9: warning: no previous prototype for `sysfs_compact_node' [-Wmissing-prototypes Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-03mm, compaction: avoid isolating pinned pagesDavid Rientjes
Page migration will fail for memory that is pinned in memory with, for example, get_user_pages(). In this case, it is unnecessary to take zone->lru_lock or isolating the page and passing it to page migration which will ultimately fail. This is a racy check, the page can still change from under us, but in that case we'll just fail later when attempting to move the page. This avoids very expensive memory compaction when faulting transparent hugepages after pinning a lot of memory with a Mellanox driver. On a 128GB machine and pinning ~120GB of memory, before this patch we see the enormous disparity in the number of page migration failures because of the pinning (from /proc/vmstat): compact_pages_moved 8450 compact_pagemigrate_failed 15614415 0.05% of pages isolated are successfully migrated and explicitly triggering memory compaction takes 102 seconds. After the patch: compact_pages_moved 9197 compact_pagemigrate_failed 7 99.9% of pages isolated are now successfully migrated in this configuration and memory compaction takes less than one second. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Hugh Dickins <hughd@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Rik van Riel <riel@redhat.com> Cc: Greg Thelen <gthelen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-03mm, compaction: ignore pageblock skip when manually invoking compactionDavid Rientjes
The cached pageblock hint should be ignored when triggering compaction through /proc/sys/vm/compact_memory so all eligible memory is isolated. Manually invoking compaction is known to be expensive, there's no need to skip pageblocks based on heuristics (mainly for debugging). Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-03-10mm/compaction: break out of loop on !PageBuddy in isolate_freepages_blockLaura Abbott
We received several reports of bad page state when freeing CMA pages previously allocated with alloc_contig_range: BUG: Bad page state in process Binder_A pfn:63202 page:d21130b0 count:0 mapcount:1 mapping: (null) index:0x7dfbf page flags: 0x40080068(uptodate|lru|active|swapbacked) Based on the page state, it looks like the page was still in use. The page flags do not make sense for the use case though. Further debugging showed that despite alloc_contig_range returning success, at least one page in the range still remained in the buddy allocator. There is an issue with isolate_freepages_block. In strict mode (which CMA uses), if any pages in the range cannot be isolated, isolate_freepages_block should return failure 0. The current check keeps track of the total number of isolated pages and compares against the size of the range: if (strict && nr_strict_required > total_isolated) total_isolated = 0; After taking the zone lock, if one of the pages in the range is not in the buddy allocator, we continue through the loop and do not increment total_isolated. If in the last iteration of the loop we isolate more than one page (e.g. last page needed is a higher order page), the check for total_isolated may pass and we fail to detect that a page was skipped. The fix is to bail out if the loop immediately if we are in strict mode. There's no benfit to continuing anyway since we need all pages to be isolated. Additionally, drop the error checking based on nr_strict_required and just check the pfn ranges. This matches with what isolate_freepages_range does. Signed-off-by: Laura Abbott <lauraa@codeaurora.org> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-23mm: improve documentation of page_orderMel Gorman
Developers occasionally try and optimise PFN scanners by using page_order but miss that in general it requires zone->lock. This has happened twice for compaction.c and rejected both times. This patch clarifies the documentation of page_order and adds a note to compaction.c why page_order is not used. [akpm@linux-foundation.org: tweaks] [lauraa@codeaurora.org: Corrected a page_zone(page)->lock reference] Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rafael Aquini <aquini@redhat.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Laura Abbott <lauraa@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-23mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGESasha Levin
Most of the VM_BUG_ON assertions are performed on a page. Usually, when one of these assertions fails we'll get a BUG_ON with a call stack and the registers. I've recently noticed based on the requests to add a small piece of code that dumps the page to various VM_BUG_ON sites that the page dump is quite useful to people debugging issues in mm. This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what VM_BUG_ON() does, also dumps the page before executing the actual BUG_ON. [akpm@linux-foundation.org: fix up includes] Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: reset scanner positions immediately when they meetVlastimil Babka
Compaction used to start its migrate and free page scaners at the zone's lowest and highest pfn, respectively. Later, caching was introduced to remember the scanners' progress across compaction attempts so that pageblocks are not re-scanned uselessly. Additionally, pageblocks where isolation failed are marked to be quickly skipped when encountered again in future compactions. Currently, both the reset of cached pfn's and clearing of the pageblock skip information for a zone is done in __reset_isolation_suitable(). This function gets called when: - compaction is restarting after being deferred - compact_blockskip_flush flag is set in compact_finished() when the scanners meet (and not again cleared when direct compaction succeeds in allocation) and kswapd acts upon this flag before going to sleep This behavior is suboptimal for several reasons: - when direct sync compaction is called after async compaction fails (in the allocation slowpath), it will effectively do nothing, unless kswapd happens to process the compact_blockskip_flush flag meanwhile. This is racy and goes against the purpose of sync compaction to more thoroughly retry the compaction of a zone where async compaction has failed. The restart-after-deferring path cannot help here as deferring happens only after the sync compaction fails. It is also done only for the preferred zone, while the compaction might be done for a fallback zone. - the mechanism of marking pageblock to be skipped has little value since the cached pfn's are reset only together with the pageblock skip flags. This effectively limits pageblock skip usage to parallel compactions. This patch changes compact_finished() so that cached pfn's are reset immediately when the scanners meet. Clearing pageblock skip flags is unchanged, as well as the other situations where cached pfn's are reset. This allows the sync-after-async compaction to retry pageblocks not marked as skipped, such as blocks !MIGRATE_MOVABLE blocks that async compactions now skips without marking them. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Rik van Riel <riel@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: do not mark unmovable pageblocks as skipped in async compactionVlastimil Babka
Compaction temporarily marks pageblocks where it fails to isolate pages as to-be-skipped in further compactions, in order to improve efficiency. One of the reasons to fail isolating pages is that isolation is not attempted in pageblocks that are not of MIGRATE_MOVABLE (or CMA) type. The problem is that blocks skipped due to not being MIGRATE_MOVABLE in async compaction become skipped due to the temporary mark also in future sync compaction. Moreover, this may follow quite soon during __alloc_page_slowpath, without much time for kswapd to clear the pageblock skip marks. This goes against the idea that sync compaction should try to scan these blocks more thoroughly than the async compaction. The fix is to ensure in async compaction that these !MIGRATE_MOVABLE blocks are not marked to be skipped. Note this should not affect performance or locking impact of further async compactions, as skipping a block due to being !MIGRATE_MOVABLE is done soon after skipping a block marked to be skipped, both without locking. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Rik van Riel <riel@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: detect when scanners meet in isolate_freepagesVlastimil Babka
Compaction of a zone is finished when the migrate scanner (which begins at the zone's lowest pfn) meets the free page scanner (which begins at the zone's highest pfn). This is detected in compact_zone() and in the case of direct compaction, the compact_blockskip_flush flag is set so that kswapd later resets the cached scanner pfn's, and a new compaction may again start at the zone's borders. The meeting of the scanners can happen during either scanner's activity. However, it may currently fail to be detected when it occurs in the free page scanner, due to two problems. First, isolate_freepages() keeps free_pfn at the highest block where it isolated pages from, for the purposes of not missing the pages that are returned back to allocator when migration fails. Second, failing to isolate enough free pages due to scanners meeting results in -ENOMEM being returned by migrate_pages(), which makes compact_zone() bail out immediately without calling compact_finished() that would detect scanners meeting. This failure to detect scanners meeting might result in repeated attempts at compaction of a zone that keep starting from the cached pfn's close to the meeting point, and quickly failing through the -ENOMEM path, without the cached pfns being reset, over and over. This has been observed (through additional tracepoints) in the third phase of the mmtests stress-highalloc benchmark, where the allocator runs on an otherwise idle system. The problem was observed in the DMA32 zone, which was used as a fallback to the preferred Normal zone, but on the 4GB system it was actually the largest zone. The problem is even amplified for such fallback zone - the deferred compaction logic, which could (after being fixed by a previous patch) reset the cached scanner pfn's, is only applied to the preferred zone and not for the fallbacks. The problem in the third phase of the benchmark was further amplified by commit 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy") which resulted in a non-deterministic regression of the allocation success rate from ~85% to ~65%. This occurs in about half of benchmark runs, making bisection problematic. It is unlikely that the commit itself is buggy, but it should put more pressure on the DMA32 zone during phases 1 and 2, which may leave it more fragmented in phase 3 and expose the bugs that this patch fixes. The fix is to make scanners meeting in isolate_freepage() stay that way, and to check in compact_zone() for scanners meeting when migrate_pages() returns -ENOMEM. The result is that compact_finished() also detects scanners meeting and sets the compact_blockskip_flush flag to make kswapd reset the scanner pfn's. The results in stress-highalloc benchmark show that the "regression" by commit 81c0a2bb515f in phase 3 no longer occurs, and phase 1 and 2 allocation success rates are also significantly improved. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: reset cached scanner pfn's before reading themVlastimil Babka
Compaction caches pfn's for its migrate and free scanners to avoid scanning the whole zone each time. In compact_zone(), the cached values are read to set up initial values for the scanners. There are several situations when these cached pfn's are reset to the first and last pfn of the zone, respectively. One of these situations is when a compaction has been deferred for a zone and is now being restarted during a direct compaction, which is also done in compact_zone(). However, compact_zone() currently reads the cached pfn's *before* resetting them. This means the reset doesn't affect the compaction that performs it, and with good chance also subsequent compactions, as update_pageblock_skip() is likely to be called and update the cached pfn's to those being processed. Another chance for a successful reset is when a direct compaction detects that migration and free scanners meet (which has its own problems addressed by another patch) and sets update_pageblock_skip flag which kswapd uses to do the reset because it goes to sleep. This is clearly a bug that results in non-deterministic behavior, so this patch moves the cached pfn reset to be performed *before* the values are read. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: encapsulate defer reset logicVlastimil Babka
Currently there are several functions to manipulate the deferred compaction state variables. The remaining case where the variables are touched directly is when a successful allocation occurs in direct compaction, or is expected to be successful in the future by kswapd. Here, the lowest order that is expected to fail is updated, and in the case of successful allocation, the deferred status and counter is reset completely. Create a new function compaction_defer_reset() to encapsulate this functionality and make it easier to understand the code. No functional change. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21mm: compaction: trace compaction begin and endMel Gorman
The broad goal of the series is to improve allocation success rates for huge pages through memory compaction, while trying not to increase the compaction overhead. The original objective was to reintroduce capturing of high-order pages freed by the compaction, before they are split by concurrent activity. However, several bugs and opportunities for simple improvements were found in the current implementation, mostly through extra tracepoints (which are however too ugly for now to be considered for sending). The patches mostly deal with two mechanisms that reduce compaction overhead, which is caching the progress of migrate and free scanners, and marking pageblocks where isolation failed to be skipped during further scans. Patch 1 (from mgorman) adds tracepoints that allow calculate time spent in compaction and potentially debug scanner pfn values. Patch 2 encapsulates the some functionality for handling deferred compactions for better maintainability, without a functional change type is not determined without being actually needed. Patch 3 fixes a bug where cached scanner pfn's are sometimes reset only after they have been read to initialize a compaction run. Patch 4 fixes a bug where scanners meeting is sometimes not properly detected and can lead to multiple compaction attempts quitting early without doing any work. Patch 5 improves the chances of sync compaction to process pageblocks that async compaction has skipped due to being !MIGRATE_MOVABLE. Patch 6 improves the chances of sync direct compaction to actually do anything when called after async compaction fails during allocation slowpath. The impact of patches were validated using mmtests's stress-highalloc benchmark with mmtests's stress-highalloc benchmark on a x86_64 machine with 4GB memory. Due to instability of the results (mostly related to the bugs fixed by patches 2 and 3), 10 iterations were performed, taking min,mean,max values for success rates and mean values for time and vmstat-based metrics. First, the default GFP_HIGHUSER_MOVABLE allocations were tested with the patches stacked on top of v3.13-rc2. Patch 2 is OK to serve as baseline due to no functional changes in 1 and 2. Comments below. stress-highalloc 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-nothp 3-nothp 4-nothp 5-nothp 6-nothp Success 1 Min 9.00 ( 0.00%) 10.00 (-11.11%) 43.00 (-377.78%) 43.00 (-377.78%) 33.00 (-266.67%) Success 1 Mean 27.50 ( 0.00%) 25.30 ( 8.00%) 45.50 (-65.45%) 45.90 (-66.91%) 46.30 (-68.36%) Success 1 Max 36.00 ( 0.00%) 36.00 ( 0.00%) 47.00 (-30.56%) 48.00 (-33.33%) 52.00 (-44.44%) Success 2 Min 10.00 ( 0.00%) 8.00 ( 20.00%) 46.00 (-360.00%) 45.00 (-350.00%) 35.00 (-250.00%) Success 2 Mean 26.40 ( 0.00%) 23.50 ( 10.98%) 47.30 (-79.17%) 47.60 (-80.30%) 48.10 (-82.20%) Success 2 Max 34.00 ( 0.00%) 33.00 ( 2.94%) 48.00 (-41.18%) 50.00 (-47.06%) 54.00 (-58.82%) Success 3 Min 65.00 ( 0.00%) 63.00 ( 3.08%) 85.00 (-30.77%) 84.00 (-29.23%) 85.00 (-30.77%) Success 3 Mean 76.70 ( 0.00%) 70.50 ( 8.08%) 86.20 (-12.39%) 85.50 (-11.47%) 86.00 (-12.13%) Success 3 Max 87.00 ( 0.00%) 86.00 ( 1.15%) 88.00 ( -1.15%) 87.00 ( 0.00%) 87.00 ( 0.00%) 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-nothp 3-nothp 4-nothp 5-nothp 6-nothp User 6437.72 6459.76 5960.32 5974.55 6019.67 System 1049.65 1049.09 1029.32 1031.47 1032.31 Elapsed 1856.77 1874.48 1949.97 1994.22 1983.15 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-nothp 3-nothp 4-nothp 5-nothp 6-nothp Minor Faults 253952267 254581900 250030122 250507333 250157829 Major Faults 420 407 506 530 530 Swap Ins 4 9 9 6 6 Swap Outs 398 375 345 346 333 Direct pages scanned 197538 189017 298574 287019 299063 Kswapd pages scanned 1809843 1801308 1846674 1873184 1861089 Kswapd pages reclaimed 1806972 1798684 1844219 1870509 1858622 Direct pages reclaimed 197227 188829 298380 286822 298835 Kswapd efficiency 99% 99% 99% 99% 99% Kswapd velocity 953.382 970.449 952.243 934.569 922.286 Direct efficiency 99% 99% 99% 99% 99% Direct velocity 104.058 101.832 153.961 143.200 148.205 Percentage direct scans 9% 9% 13% 13% 13% Zone normal velocity 347.289 359.676 348.063 339.933 332.983 Zone dma32 velocity 710.151 712.605 758.140 737.835 737.507 Zone dma velocity 0.000 0.000 0.000 0.000 0.000 Page writes by reclaim 557.600 429.000 353.600 426.400 381.800 Page writes file 159 53 7 79 48 Page writes anon 398 375 345 346 333 Page reclaim immediate 825 644 411 575 420 Sector Reads 2781750 2769780 2878547 2939128 2910483 Sector Writes 12080843 12083351 12012892 12002132 12010745 Page rescued immediate 0 0 0 0 0 Slabs scanned 1575654 1545344 1778406 1786700 1794073 Direct inode steals 9657 10037 15795 14104 14645 Kswapd inode steals 46857 46335 50543 50716 51796 Kswapd skipped wait 0 0 0 0 0 THP fault alloc 97 91 81 71 77 THP collapse alloc 456 506 546 544 565 THP splits 6 5 5 4 4 THP fault fallback 0 1 0 0 0 THP collapse fail 14 14 12 13 12 Compaction stalls 1006 980 1537 1536 1548 Compaction success 303 284 562 559 578 Compaction failures 702 696 974 976 969 Page migrate success 1177325 1070077 3927538 3781870 3877057 Page migrate failure 0 0 0 0 0 Compaction pages isolated 2547248 2306457 8301218 8008500 8200674 Compaction migrate scanned 42290478 38832618 153961130 154143900 159141197 Compaction free scanned 89199429 79189151 356529027 351943166 356326727 Compaction cost 1566 1426 5312 5156 5294 NUMA PTE updates 0 0 0 0 0 NUMA hint faults 0 0 0 0 0 NUMA hint local faults 0 0 0 0 0 NUMA hint local percent 100 100 100 100 100 NUMA pages migrated 0 0 0 0 0 AutoNUMA cost 0 0 0 0 0 Observations: - The "Success 3" line is allocation success rate with system idle (phases 1 and 2 are with background interference). I used to get stable values around 85% with vanilla 3.11. The lower min and mean values came with 3.12. This was bisected to commit 81c0a2bb ("mm: page_alloc: fair zone allocator policy") As explained in comment for patch 3, I don't think the commit is wrong, but that it makes the effect of compaction bugs worse. From patch 3 onwards, the results are OK and match the 3.11 results. - Patch 4 also clearly helps phases 1 and 2, and exceeds any results I've seen with 3.11 (I didn't measure it that thoroughly then, but it was never above 40%). - Compaction cost and number of scanned pages is higher, especially due to patch 4. However, keep in mind that patches 3 and 4 fix existing bugs in the current design of compaction overhead mitigation, they do not change it. If overhead is found unacceptable, then it should be decreased differently (and consistently, not due to random conditions) than the current implementation does. In contrast, patches 5 and 6 (which are not strictly bug fixes) do not increase the overhead (but also not success rates). This might be a limitation of the stress-highalloc benchmark as it's quite uniform. Another set of results is when configuring stress-highalloc t allocate with similar flags as THP uses: (GFP_HIGHUSER_MOVABLE|__GFP_NOMEMALLOC|__GFP_NORETRY|__GFP_NO_KSWAPD) stress-highalloc 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-thp 3-thp 4-thp 5-thp 6-thp Success 1 Min 2.00 ( 0.00%) 7.00 (-250.00%) 18.00 (-800.00%) 19.00 (-850.00%) 26.00 (-1200.00%) Success 1 Mean 19.20 ( 0.00%) 17.80 ( 7.29%) 29.20 (-52.08%) 29.90 (-55.73%) 32.80 (-70.83%) Success 1 Max 27.00 ( 0.00%) 29.00 ( -7.41%) 35.00 (-29.63%) 36.00 (-33.33%) 37.00 (-37.04%) Success 2 Min 3.00 ( 0.00%) 8.00 (-166.67%) 21.00 (-600.00%) 21.00 (-600.00%) 32.00 (-966.67%) Success 2 Mean 19.30 ( 0.00%) 17.90 ( 7.25%) 32.20 (-66.84%) 32.60 (-68.91%) 35.70 (-84.97%) Success 2 Max 27.00 ( 0.00%) 30.00 (-11.11%) 36.00 (-33.33%) 37.00 (-37.04%) 39.00 (-44.44%) Success 3 Min 62.00 ( 0.00%) 62.00 ( 0.00%) 85.00 (-37.10%) 75.00 (-20.97%) 64.00 ( -3.23%) Success 3 Mean 66.30 ( 0.00%) 65.50 ( 1.21%) 85.60 (-29.11%) 83.40 (-25.79%) 83.50 (-25.94%) Success 3 Max 70.00 ( 0.00%) 69.00 ( 1.43%) 87.00 (-24.29%) 86.00 (-22.86%) 87.00 (-24.29%) 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-thp 3-thp 4-thp 5-thp 6-thp User 6547.93 6475.85 6265.54 6289.46 6189.96 System 1053.42 1047.28 1043.23 1042.73 1038.73 Elapsed 1835.43 1821.96 1908.67 1912.74 1956.38 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 3.13-rc2 2-thp 3-thp 4-thp 5-thp 6-thp Minor Faults 256805673 253106328 253222299 249830289 251184418 Major Faults 395 375 423 434 448 Swap Ins 12 10 10 12 9 Swap Outs 530 537 487 455 415 Direct pages scanned 71859 86046 153244 152764 190713 Kswapd pages scanned 1900994 1870240 1898012 1892864 1880520 Kswapd pages reclaimed 1897814 1867428 1894939 1890125 1877924 Direct pages reclaimed 71766 85908 153167 152643 190600 Kswapd efficiency 99% 99% 99% 99% 99% Kswapd velocity 1029.000 1067.782 1000.091 991.049 951.218 Direct efficiency 99% 99% 99% 99% 99% Direct velocity 38.897 49.127 80.747 79.983 96.468 Percentage direct scans 3% 4% 7% 7% 9% Zone normal velocity 351.377 372.494 348.910 341.689 335.310 Zone dma32 velocity 716.520 744.414 731.928 729.343 712.377 Zone dma velocity 0.000 0.000 0.000 0.000 0.000 Page writes by reclaim 669.300 604.000 545.700 538.900 429.900 Page writes file 138 66 58 83 14 Page writes anon 530 537 487 455 415 Page reclaim immediate 806 655 772 548 517 Sector Reads 2711956 2703239 2811602 2818248 2839459 Sector Writes 12163238 12018662 12038248 11954736 11994892 Page rescued immediate 0 0 0 0 0 Slabs scanned 1385088 1388364 1507968 1513292 1558656 Direct inode steals 1739 2564 4622 5496 6007 Kswapd inode steals 47461 46406 47804 48013 48466 Kswapd skipped wait 0 0 0 0 0 THP fault alloc 110 82 84 69 70 THP collapse alloc 445 482 467 462 539 THP splits 6 5 4 5 3 THP fault fallback 3 0 0 0 0 THP collapse fail 15 14 14 14 13 Compaction stalls 659 685 1033 1073 1111 Compaction success 222 225 410 427 456 Compaction failures 436 460 622 646 655 Page migrate success 446594 439978 1085640 1095062 1131716 Page migrate failure 0 0 0 0 0 Compaction pages isolated 1029475 1013490 2453074 2482698 2565400 Compaction migrate scanned 9955461 11344259 24375202 27978356 30494204 Compaction free scanned 27715272 28544654 80150615 82898631 85756132 Compaction cost 552 555 1344 1379 1436 NUMA PTE updates 0 0 0 0 0 NUMA hint faults 0 0 0 0 0 NUMA hint local faults 0 0 0 0 0 NUMA hint local percent 100 100 100 100 100 NUMA pages migrated 0 0 0 0 0 AutoNUMA cost 0 0 0 0 0 There are some differences from the previous results for THP-like allocations: - Here, the bad result for unpatched kernel in phase 3 is much more consistent to be between 65-70% and not related to the "regression" in 3.12. Still there is the improvement from patch 4 onwards, which brings it on par with simple GFP_HIGHUSER_MOVABLE allocations. - Compaction costs have increased, but nowhere near as much as the non-THP case. Again, the patches should be worth the gained determininsm. - Patches 5 and 6 somewhat increase the number of migrate-scanned pages. This is most likely due to __GFP_NO_KSWAPD flag, which means the cached pfn's and pageblock skip bits are not reset by kswapd that often (at least in phase 3 where no concurrent activity would wake up kswapd) and the patches thus help the sync-after-async compaction. It doesn't however show that the sync compaction would help so much with success rates, which can be again seen as a limitation of the benchmark scenario. This patch (of 6): Add two tracepoints for compaction begin and end of a zone. Using this it is possible to calculate how much time a workload is spending within compaction and potentially debug problems related to cached pfns for scanning. In combination with the direct reclaim and slab trace points it should be possible to estimate most allocation-related overhead for a workload. Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Rik van Riel <riel@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-12-18mm/compaction: respect ignore_skip_hint in update_pageblock_skipJoonsoo Kim
update_pageblock_skip() only fits to compaction which tries to isolate by pageblock unit. If isolate_migratepages_range() is called by CMA, it try to isolate regardless of pageblock unit and it don't reference get_pageblock_skip() by ignore_skip_hint. We should also respect it on update_pageblock_skip() to prevent from setting the wrong information. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rafael Aquini <aquini@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Cc: <stable@vger.kernel.org> [3.7+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-11-13mm/compaction.c: update comment about zone lock in isolate_freepages_blockJerome Marchand
Since commit f40d1e42bb98 ("mm: compaction: acquire the zone->lock as late as possible"), isolate_freepages_block() takes the zone->lock itself. The function description however still states that the zone->lock must be held. This patch removes this outdated statement. Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30mm/compaction.c: periodically schedule when freeing pagesDavid Rientjes
We've been getting warnings about an excessive amount of time spent allocating pages for migration during memory compaction without scheduling. isolate_freepages_block() already periodically checks for contended locks or the need to schedule, but isolate_freepages() never does. When a zone is massively long and no suitable targets can be found, this iteration can be quite expensive without ever doing cond_resched(). Check periodically for the need to reschedule while the compaction free scanner iterates. Signed-off-by: David Rientjes <rientjes@google.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-11mm: compaction: do not compact pgdat for order-0Mel Gorman
If kswapd was reclaiming for a high order and resets it to 0 due to fragmentation it will still call compact_pgdat. For the most part, this will fail a compaction_suitable() test and not compact but it is unnecessarily sloppy. It could be fixed in the caller but fix it in the API instead. [dhillf@gmail.com: pointed out that it was a potential problem] Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Hillf Danton <dhillf@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23mm: add & use zone_end_pfn() and zone_spans_pfn()Cody P Schafer
Add 2 helpers (zone_end_pfn() and zone_spans_pfn()) to reduce code duplication. This also switches to using them in compaction (where an additional variable needed to be renamed), page_alloc, vmstat, memory_hotplug, and kmemleak. Note that in compaction.c I avoid calling zone_end_pfn() repeatedly because I expect at some point the sycronization issues with start_pfn & spanned_pages will need fixing, either by actually using the seqlock or clever memory barrier usage. Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com> Cc: David Hansen <dave@linux.vnet.ibm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23mm: remove offlining arg to migrate_pagesHugh Dickins
No functional change, but the only purpose of the offlining argument to migrate_pages() etc, was to ensure that __unmap_and_move() could migrate a KSM page for memory hotremove (which took ksm_thread_mutex) but not for other callers. Now all cases are safe, remove the arg. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Petr Holasek <pholasek@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23mm: remove MIGRATE_ISOLATE check in hotpathMinchan Kim
Several functions test MIGRATE_ISOLATE and some of those are hotpath but MIGRATE_ISOLATE is used only if we enable CONFIG_MEMORY_ISOLATION(ie, CMA, memory-hotplug and memory-failure) which are not common config option. So let's not add unnecessary overhead and code when we don't enable CONFIG_MEMORY_ISOLATION. Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23mm: compaction: make __compact_pgdat() and compact_pgdat() return voidAndrew Morton
These functions always return 0. Formalise this. Cc: Jason Liu <r64343@freescale.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23mm: compaction: do not accidentally skip pageblocks in the migrate scannerMel Gorman
Compaction uses the ALIGN macro incorrectly with the migrate scanner by adding pageblock_nr_pages to a PFN. It happened to work when initially implemented as the starting PFN was also aligned but with caching restarts and isolating in smaller chunks this is no longer always true. The impact is that the migrate scanner scans outside its current pageblock. As pfn_valid() is still checked properly it does not cause any failure and the impact of the bug is that in some cases it will scan more than necessary when it crosses a page boundary but by no more than COMPACT_CLUSTER_MAX. It is highly unlikely this is even measurable but it's still wrong so this patch addresses the problem. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-01-11mm: compaction: partially revert capture of suitable high-order pageMel Gorman
Eric Wong reported on 3.7 and 3.8-rc2 that ppoll() got stuck when waiting for POLLIN on a local TCP socket. It was easier to trigger if there was disk IO and dirty pages at the same time and he bisected it to commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available"). The intention of that patch was to improve high-order allocations under memory pressure after changes made to reclaim in 3.6 drastically hurt THP allocations but the approach was flawed. For Eric, the problem was that page->pfmemalloc was not being cleared for captured pages leading to a poor interaction with swap-over-NFS support causing the packets to be dropped. However, I identified a few more problems with the patch including the fact that it can increase contention on zone->lock in some cases which could result in async direct compaction being aborted early. In retrospect the capture patch took the wrong approach. What it should have done is mark the pageblock being migrated as MIGRATE_ISOLATE if it was allocating for THP and avoided races that way. While the patch was showing to improve allocation success rates at the time, the benefit is marginal given the relative complexity and it should be revisited from scratch in the context of the other reclaim-related changes that have taken place since the patch was first written and tested. This patch partially reverts commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available"). Reported-and-tested-by: Eric Wong <normalperson@yhbt.net> Tested-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: David Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-01-11mm: compaction: fix echo 1 > compact_memory return error issueJason Liu
when run the folloing command under shell, it will return error sh/$ echo 1 > /proc/sys/vm/compact_memory sh/$ sh: write error: Bad address After strace, I found the following log: ... write(1, "1\n", 2) = 3 write(1, "", 4294967295) = -1 EFAULT (Bad address) write(2, "echo: write error: Bad address\n", 31echo: write error: Bad address ) = 31 This tells system return 3(COMPACT_COMPLETE) after write data to compact_memory. The fix is to make the system just return 0 instead 3(COMPACT_COMPLETE) from sysctl_compaction_handler after compaction_nodes finished. Signed-off-by: Jason Liu <r64343@freescale.com> Suggested-by: David Rientjes <rientjes@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: David Rientjes <rientjes@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-20compaction: fix build error in CMA && !COMPACTIONMinchan Kim
isolate_freepages_block() and isolate_migratepages_range() are used for CMA as well as compaction so it breaks build for CONFIG_CMA && !CONFIG_COMPACTION. This patch fixes it. [akpm@linux-foundation.org: add "do { } while (0)", per Mel] Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-16Merge tag 'balancenuma-v11' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma Pull Automatic NUMA Balancing bare-bones from Mel Gorman: "There are three implementations for NUMA balancing, this tree (balancenuma), numacore which has been developed in tip/master and autonuma which is in aa.git. In almost all respects balancenuma is the dumbest of the three because its main impact is on the VM side with no attempt to be smart about scheduling. In the interest of getting the ball rolling, it would be desirable to see this much merged for 3.8 with the view to building scheduler smarts on top and adapting the VM where required for 3.9. The most recent set of comparisons available from different people are mel: https://lkml.org/lkml/2012/12/9/108 mingo: https://lkml.org/lkml/2012/12/7/331 tglx: https://lkml.org/lkml/2012/12/10/437 srikar: https://lkml.org/lkml/2012/12/10/397 The results are a mixed bag. In my own tests, balancenuma does reasonably well. It's dumb as rocks and does not regress against mainline. On the other hand, Ingo's tests shows that balancenuma is incapable of converging for this workloads driven by perf which is bad but is potentially explained by the lack of scheduler smarts. Thomas' results show balancenuma improves on mainline but falls far short of numacore or autonuma. Srikar's results indicate we all suffer on a large machine with imbalanced node sizes. My own testing showed that recent numacore results have improved dramatically, particularly in the last week but not universally. We've butted heads heavily on system CPU usage and high levels of migration even when it shows that overall performance is better. There are also cases where it regresses. Of interest is that for specjbb in some configurations it will regress for lower numbers of warehouses and show gains for higher numbers which is not reported by the tool by default and sometimes missed in treports. Recently I reported for numacore that the JVM was crashing with NullPointerExceptions but currently it's unclear what the source of this problem is. Initially I thought it was in how numacore batch handles PTEs but I'm no longer think this is the case. It's possible numacore is just able to trigger it due to higher rates of migration. These reports were quite late in the cycle so I/we would like to start with this tree as it contains much of the code we can agree on and has not changed significantly over the last 2-3 weeks." * tag 'balancenuma-v11' of git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma: (50 commits) mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable mm/rmap: Convert the struct anon_vma::mutex to an rwsem mm: migrate: Account a transhuge page properly when rate limiting mm: numa: Account for failed allocations and isolations as migration failures mm: numa: Add THP migration for the NUMA working set scanning fault case build fix mm: numa: Add THP migration for the NUMA working set scanning fault case. mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node mm: sched: numa: Control enabling and disabling of NUMA balancing if !SCHED_DEBUG mm: sched: numa: Control enabling and disabling of NUMA balancing mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate mm: numa: Use a two-stage filter to restrict pages being migrated for unlikely task<->node relationships mm: numa: migrate: Set last_nid on newly allocated page mm: numa: split_huge_page: Transfer last_nid on tail page mm: numa: Introduce last_nid to the page frame sched: numa: Slowly increase the scanning period as NUMA faults are handled mm: numa: Rate limit setting of pte_numa if node is saturated mm: numa: Rate limit the amount of memory that is migrated between nodes mm: numa: Structures for Migrate On Fault per NUMA migration rate limiting mm: numa: Migrate pages handled during a pmd_numa hinting fault mm: numa: Migrate on reference policy ...
2012-12-12mm: compaction: Fix compiler warningThierry Reding
compact_capture_page() is only used if compaction is enabled so it should be moved into the corresponding #ifdef. Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-11mm: introduce putback_movable_pages()Rafael Aquini
The PATCH "mm: introduce compaction and migration for virtio ballooned pages" hacks around putback_lru_pages() in order to allow ballooned pages to be re-inserted on balloon page list as if a ballooned page was like a LRU page. As ballooned pages are not legitimate LRU pages, this patch introduces putback_movable_pages() to properly cope with cases where the isolated pageset contains ballooned pages and LRU pages, thus fixing the mentioned inelegant hack around putback_lru_pages(). Signed-off-by: Rafael Aquini <aquini@redhat.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andi Kleen <andi@firstfloor.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-11mm: introduce compaction and migration for ballooned pagesRafael Aquini
Memory fragmentation introduced by ballooning might reduce significantly the number of 2MB contiguous memory blocks that can be used within a guest, thus imposing performance penalties associated with the reduced number of transparent huge pages that could be used by the guest workload. This patch introduces the helper functions as well as the necessary changes to teach compaction and migration bits how to cope with pages which are part of a guest memory balloon, in order to make them movable by memory compaction procedures. Signed-off-by: Rafael Aquini <aquini@redhat.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-11mm: compaction: Add scanned and isolated counters for compactionMel Gorman
Compaction already has tracepoints to count scanned and isolated pages but it requires that ftrace be enabled and if that information has to be written to disk then it can be disruptive. This patch adds vmstat counters for compaction called compact_migrate_scanned, compact_free_scanned and compact_isolated. With these counters, it is possible to define a basic cost model for compaction. This approximates of how much work compaction is doing and can be compared that with an oprofile showing TLB misses and see if the cost of compaction is being offset by THP for example. Minimally a compaction patch can be evaluated in terms of whether it increases or decreases cost. The basic cost model looks like this Fundamental unit u: a word sizeof(void *) Ca = cost of struct page access = sizeof(struct page) / u Cmc = Cost migrate page copy = (Ca + PAGE_SIZE/u) * 2 Cmf = Cost migrate failure = Ca * 2 Ci = Cost page isolation = (Ca + Wi) where Wi is a constant that should reflect the approximate cost of the locking operation. Csm = Cost migrate scanning = Ca Csf = Cost free scanning = Ca Overall cost = (Csm * compact_migrate_scanned) + (Csf * compact_free_scanned) + (Ci * compact_isolated) + (Cmc * pgmigrate_success) + (Cmf * pgmigrate_failed) Where the values are read from /proc/vmstat. This is very basic and ignores certain costs such as the allocation cost to do a migrate page copy but any improvement to the model would still use the same vmstat counters. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11mm: migrate: Add a tracepoint for migrate_pagesMel Gorman
The pgmigrate_success and pgmigrate_fail vmstat counters tells the user about migration activity but not the type or the reason. This patch adds a tracepoint to identify the type of page migration and why the page is being migrated. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11mm: compaction: Move migration fail/success stats to migrate.cMel Gorman
The compact_pages_moved and compact_pagemigrate_failed events are convenient for determining if compaction is active and to what degree migration is succeeding but it's at the wrong level. Other users of migration may also want to know if migration is working properly and this will be particularly true for any automated NUMA migration. This patch moves the counters down to migration with the new events called pgmigrate_success and pgmigrate_fail. The compact_blocks_moved counter is removed because while it was useful for debugging initially, it's worthless now as no meaningful conclusions can be drawn from its value. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-06mm: compaction: validate pfn range passed to isolate_freepages_blockMel Gorman
Commit 0bf380bc70ec ("mm: compaction: check pfn_valid when entering a new MAX_ORDER_NR_PAGES block during isolation for migration") added a check for pfn_valid() when isolating pages for migration as the scanner does not necessarily start pageblock-aligned. Since commit c89511ab2f8f ("mm: compaction: Restart compaction from near where it left off"), the free scanner has the same problem. This patch makes sure that the pfn range passed to isolate_freepages_block() is within the same block so that pfn_valid() checks are unnecessary. In answer to Henrik's wondering why others have not reported this: reproducing this requires a large enough hole with the right aligment to have compaction walk into a PFN range with no memmap. Size and alignment depends in the memory model - 4M for FLATMEM and 128M for SPARSEMEM on x86. It needs a "lucky" machine. Reported-by: Henrik Rydberg <rydberg@euromail.se> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-19mm: compaction: correct the nr_strict va isolated check for CMAMel Gorman
Thierry reported that the "iron out" patch for isolate_freepages_block() had problems due to the strict check being too strict with "mm: compaction: Iron out isolate_freepages_block() and isolate_freepages_range() -fix1". It's possible that more pages than necessary are isolated but the check still fails and I missed that this fix was not picked up before RC1. This same problem has been identified in 3.7-RC1 by Tony Prisk and should be addressed by the following patch. Signed-off-by: Mel Gorman <mgorman@suse.de> Tested-by: Tony Prisk <linux@prisktech.co.nz> Reported-by: Thierry Reding <thierry.reding@avionic-design.de> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Richard Davies <richard@arachsys.com> Cc: Shaohua Li <shli@kernel.org> Cc: Avi Kivity <avi@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>