From cf66f0700c8f1d7c7c1c1d7e5e846a1836814601 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:45:24 -0800 Subject: [PATCH] mm, compaction: do not consider a need to reschedule as contention Scanning on large machines can take a considerable length of time and eventually need to be rescheduled. This is treated as an abort event but that's not appropriate as the attempt is likely to be retried after making numerous checks and taking another cycle through the page allocator. This patch will check the need to reschedule if necessary but continue the scanning. The main benefit is reduced scanning when compaction is taking a long time or the machine is over-saturated. It also avoids an unnecessary exit of compaction that ends up being retried by the page allocator in the outer loop. 5.0.0-rc1 5.0.0-rc1 synccached-v3r16 noresched-v3r17 Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* Amean fault-both-3 2958.27 ( 0.00%) 2965.68 ( -0.25%) Amean fault-both-5 4091.90 ( 0.00%) 3995.90 ( 2.35%) Amean fault-both-7 5803.05 ( 0.00%) 5842.12 ( -0.67%) Amean fault-both-12 9481.06 ( 0.00%) 9550.87 ( -0.74%) Amean fault-both-18 14141.51 ( 0.00%) 13304.72 ( 5.92%) Amean fault-both-24 16438.00 ( 0.00%) 14618.59 ( 11.07%) Amean fault-both-30 17531.72 ( 0.00%) 16650.96 ( 5.02%) Amean fault-both-32 17101.96 ( 0.00%) 17145.15 ( -0.25%) Link: http://lkml.kernel.org/r/20190118175136.31341-18-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: Dan Carpenter Cc: David Rientjes Cc: YueHaibing Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 23 ++++------------------- 1 file changed, 4 insertions(+), 19 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 68e3c214bcbd..9c7d43fd4655 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -404,21 +404,6 @@ static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags, return true; } -/* - * Aside from avoiding lock contention, compaction also periodically checks - * need_resched() and records async compaction as contended if necessary. - */ -static inline void compact_check_resched(struct compact_control *cc) -{ - /* async compaction aborts if contended */ - if (need_resched()) { - if (cc->mode == MIGRATE_ASYNC) - cc->contended = true; - - cond_resched(); - } -} - /* * Compaction requires the taking of some coarse locks that are potentially * very heavily contended. The lock should be periodically unlocked to avoid @@ -447,7 +432,7 @@ static bool compact_unlock_should_abort(spinlock_t *lock, return true; } - compact_check_resched(cc); + cond_resched(); return false; } @@ -736,7 +721,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, return 0; } - compact_check_resched(cc); + cond_resched(); if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { skip_on_failure = true; @@ -1370,7 +1355,7 @@ static void isolate_freepages(struct compact_control *cc) * suitable migration targets, so periodically check resched. */ if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))) - compact_check_resched(cc); + cond_resched(); page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, zone); @@ -1666,7 +1651,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, * need to schedule. */ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))) - compact_check_resched(cc); + cond_resched(); page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, zone);