diff options
| author | Johannes Weiner <hannes@cmpxchg.org> | 2017-01-25 10:52:49 +1100 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2017-01-25 13:51:20 +1100 |
| commit | 3d95036663ad986ac633e51f3054169663d050cf (patch) | |
| tree | b3ff9664e42781c135c5f2c595ca49ddc27a1590 /mm | |
| parent | 8d433c48a8f0ee66ea4d563ae2cd7227dc69010f (diff) | |
mm: vmscan: kick flushers when we encounter dirty pages on the LRU
Memory pressure can put dirty pages at the end of the LRU without anybody
running into dirty limits. Don't start writing individual pages from
kswapd while the flushers might be asleep.
Link: http://lkml.kernel.org/r/20170123181641.23938-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmscan.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 0d05f7f3b532..56ea8d24041f 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1798,12 +1798,20 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, /* * If dirty pages are scanned that are not queued for IO, it - * implies that flushers are not keeping up. In this case, flag - * the pgdat PGDAT_DIRTY and kswapd will start writing pages from - * reclaim context. + * implies that flushers are not doing their job. This can + * happen when memory pressure pushes dirty pages to the end + * of the LRU without the dirty limits being breached. It can + * also happen when the proportion of dirty pages grows not + * through writes but through memory pressure reclaiming all + * the clean cache. And in some cases, the flushers simply + * cannot keep up with the allocation rate. Nudge the flusher + * threads in case they are asleep, but also allow kswapd to + * start writing pages during reclaim. */ - if (stat.nr_unqueued_dirty == nr_taken) + if (stat.nr_unqueued_dirty == nr_taken) { + wakeup_flusher_threads(0, WB_REASON_VMSCAN); set_bit(PGDAT_DIRTY, &pgdat->flags); + } /* * If kswapd scans pages marked marked for immediate @@ -2787,7 +2795,7 @@ retry: writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; if (total_scanned > writeback_threshold) { wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, - WB_REASON_TRY_TO_FREE_PAGES); + WB_REASON_VMSCAN); sc->may_writepage = 1; } } while (--sc->priority >= 0); |