From d818fca1cac31b1fc9301bda83e195a46fb4ebaa Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Fri, 5 Nov 2021 13:42:29 -0700 Subject: mm/vmscan: throttle reclaim and compaction when too may pages are isolated Page reclaim throttles on congestion if too many parallel reclaim instances have isolated too many pages. This makes no sense, excessive parallelisation has nothing to do with writeback or congestion. This patch creates an additional workqueue to sleep on when too many pages are isolated. The throttled tasks are woken when the number of isolated pages is reduced or a timeout occurs. There may be some false positive wakeups for GFP_NOIO/GFP_NOFS callers but the tasks will throttle again if necessary. [shy828301@gmail.com: Wake up from compaction context] [vbabka@suse.cz: Account number of throttled tasks only for writeback] Link: https://lkml.kernel.org/r/20211022144651.19914-3-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Cc: Andreas Dilger Cc: "Darrick J . Wong" Cc: Dave Chinner Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Matthew Wilcox Cc: Michal Hocko Cc: NeilBrown Cc: Rik van Riel Cc: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'mm/compaction.c') diff --git a/mm/compaction.c b/mm/compaction.c index bfc93da1c2c7..7359093d8ac0 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -761,6 +761,8 @@ isolate_freepages_range(struct compact_control *cc, /* Similar to reclaim, but different enough that they don't share logic */ static bool too_many_isolated(pg_data_t *pgdat) { + bool too_many; + unsigned long active, inactive, isolated; inactive = node_page_state(pgdat, NR_INACTIVE_FILE) + @@ -770,7 +772,11 @@ static bool too_many_isolated(pg_data_t *pgdat) isolated = node_page_state(pgdat, NR_ISOLATED_FILE) + node_page_state(pgdat, NR_ISOLATED_ANON); - return isolated > (inactive + active) / 2; + too_many = isolated > (inactive + active) / 2; + if (!too_many) + wake_throttle_isolated(pgdat); + + return too_many; } /** @@ -822,7 +828,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (cc->mode == MIGRATE_ASYNC) return -EAGAIN; - congestion_wait(BLK_RW_ASYNC, HZ/10); + reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED, HZ/10); if (fatal_signal_pending(current)) return -EINTR; -- cgit v1.2.3 From c3f4a9a2b082c5392fbff17c6d8551154add5fdb Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Fri, 5 Nov 2021 13:42:42 -0700 Subject: mm/vmscan: centralise timeout values for reclaim_throttle Neil Brown raised concerns about callers of reclaim_throttle specifying a timeout value. The original timeout values to congestion_wait() were probably pulled out of thin air or copy&pasted from somewhere else. This patch centralises the timeout values and selects a timeout based on the reason for reclaim throttling. These figures are also pulled out of the same thin air but better values may be derived Running a workload that is throttling for inappropriate periods and tracing mm_vmscan_throttled can be used to pick a more appropriate value. Excessive throttling would pick a lower timeout where as excessive CPU usage in reclaim context would select a larger timeout. Ideally a large value would always be used and the wakeups would occur before a timeout but that requires careful testing. Link: https://lkml.kernel.org/r/20211022144651.19914-7-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Cc: Andreas Dilger Cc: "Darrick J . Wong" Cc: Dave Chinner Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Matthew Wilcox Cc: Michal Hocko Cc: NeilBrown Cc: Rik van Riel Cc: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/compaction.c') diff --git a/mm/compaction.c b/mm/compaction.c index 7359093d8ac0..151b04c4dab3 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -828,7 +828,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (cc->mode == MIGRATE_ASYNC) return -EAGAIN; - reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED, HZ/10); + reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED); if (fatal_signal_pending(current)) return -EINTR; -- cgit v1.2.3