Commit 2dbf3faf authored Apr 01, 2024 by Baolin Wang Committed by Liu Shixin Apr 01, 2024

mm: compaction: update the cc->nr_migratepages when allocating or freeing the freepages

mainline inclusion
from mainline-v6.9-rc1
commit ab755bf4249b992fc2140d615ab0a686d50765b4
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I9CXS6
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ab755bf4249b992fc2140d615ab0a686d50765b4

--------------------------------

Currently we will use 'cc->nr_freepages >= cc->nr_migratepages' comparison
to ensure that enough freepages are isolated in isolate_freepages(),
however it just decreases the cc->nr_freepages without updating
cc->nr_migratepages in compaction_alloc(), which will waste more CPU
cycles and cause too many freepages to be isolated.

So we should also update the cc->nr_migratepages when allocating or
freeing the freepages to avoid isolating excess freepages.  And I can see
fewer free pages are scanned and isolated when running thpcompact on my
Arm64 server:

                                       k6.7         k6.7_patched
Ops Compaction pages isolated      120692036.00   118160797.00
Ops Compaction migrate scanned     131210329.00   154093268.00
Ops Compaction free scanned       1090587971.00  1080632536.00
Ops Compact scan efficiency               12.03          14.26

Moreover, I did not see an obvious latency improvements, this is likely
because isolating freepages is not the bottleneck in the thpcompact test
case.

                              k6.7                  k6.7_patched
Amean     fault-both-1      1089.76 (   0.00%)     1080.16 *   0.88%*
Amean     fault-both-3      1616.48 (   0.00%)     1636.65 *  -1.25%*
Amean     fault-both-5      2266.66 (   0.00%)     2219.20 *   2.09%*
Amean     fault-both-7      2909.84 (   0.00%)     2801.90 *   3.71%*
Amean     fault-both-12     4861.26 (   0.00%)     4733.25 *   2.63%*
Amean     fault-both-18     7351.11 (   0.00%)     6950.51 *   5.45%*
Amean     fault-both-24     9059.30 (   0.00%)     9159.99 *  -1.11%*
Amean     fault-both-30    10685.68 (   0.00%)    11399.02 *  -6.68%*

Link: https://lkml.kernel.org/r/6440493f18da82298152b6305d6b41c2962a3ce6.1708409245.git.baolin.wang@linux.alibaba.com


Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Liu Shixin <liushixin2@huawei.com>

parent 2ed87820

include/trace/events/compaction.h

+3 −3

Original line number	Diff line number	Diff line
		@@ -78,10 +78,10 @@ DEFINE_EVENT(mm_compaction_isolate_template, mm_compaction_fast_isolate_freepage
		#ifdef CONFIG_COMPACTION
		TRACE_EVENT(mm_compaction_migratepages,

		TP_PROTO(struct compact_control *cc,
		TP_PROTO(unsigned int nr_migratepages,
		unsigned int nr_succeeded),

		TP_ARGS(cc, nr_succeeded),
		TP_ARGS(nr_migratepages, nr_succeeded),

		TP_STRUCT__entry(
		__field(unsigned long, nr_migrated)
		@@ -90,7 +90,7 @@ TRACE_EVENT(mm_compaction_migratepages,

		TP_fast_assign(
		__entry->nr_migrated = nr_succeeded;
		__entry->nr_failed = cc->nr_migratepages - nr_succeeded;
		__entry->nr_failed = nr_migratepages - nr_succeeded;
		),

		TP_printk("nr_migrated=%lu nr_failed=%lu",

mm/compaction.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -1778,6 +1778,7 @@ static struct folio compaction_alloc(struct folio src, unsigned long data)
		dst = list_entry(cc->freepages.next, struct folio, lru);
		list_del(&dst->lru);
		cc->nr_freepages--;
		cc->nr_migratepages--;

		return dst;
		}
		@@ -1793,6 +1794,7 @@ static void compaction_free(struct folio *dst, unsigned long data)

		list_add(&dst->lru, &cc->freepages);
		cc->nr_freepages++;
		cc->nr_migratepages++;
		}

		/* possible outcome of isolate_migratepages */
		@@ -2418,7 +2420,7 @@ compact_zone(struct compact_control cc, struct capture_control capc)
		unsigned long last_migrated_pfn;
		const bool sync = cc->mode != MIGRATE_ASYNC;
		bool update_cached;
		unsigned int nr_succeeded = 0;
		unsigned int nr_succeeded = 0, nr_migratepages;

		/*
		* These counters track activities during zone compaction. Initialize
		@@ -2536,11 +2538,17 @@ compact_zone(struct compact_control cc, struct capture_control capc)
		pageblock_start_pfn(cc->migrate_pfn - 1));
		}

		/*
		* Record the number of pages to migrate since the
		* compaction_alloc/free() will update cc->nr_migratepages
		* properly.
		*/
		nr_migratepages = cc->nr_migratepages;
		err = migrate_pages(&cc->migratepages, compaction_alloc,
		compaction_free, (unsigned long)cc, cc->mode,
		MR_COMPACTION, &nr_succeeded);

		trace_mm_compaction_migratepages(cc, nr_succeeded);
		trace_mm_compaction_migratepages(nr_migratepages, nr_succeeded);

		/* All pages were either migrated or will be released */
		cc->nr_migratepages = 0;