From: Baolin Wang baolin.wang@linux.alibaba.com
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/?i...
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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/6440493f18da82298152b6305d6b41c2962a3ce6.170840924... 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 --- include/trace/events/compaction.h | 6 +++--- mm/compaction.c | 12 ++++++++++-- 2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h index 2b2a975efd20..d05759d18538 100644 --- a/include/trace/events/compaction.h +++ b/include/trace/events/compaction.h @@ -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", diff --git a/mm/compaction.c b/mm/compaction.c index 3df971352e05..923c9a480ea8 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -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;