On Mon 23-01-17 13:16:38, Johannes Weiner wrote: > 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. > > Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: Michal Hocko <[email protected]> > --- > include/linux/writeback.h | 2 +- > include/trace/events/writeback.h | 2 +- > mm/vmscan.c | 18 +++++++++++++----- > 3 files changed, 15 insertions(+), 7 deletions(-) > > diff --git a/include/linux/writeback.h b/include/linux/writeback.h > index 5527d910ba3d..a3c0cbd7c888 100644 > --- a/include/linux/writeback.h > +++ b/include/linux/writeback.h > @@ -46,7 +46,7 @@ enum writeback_sync_modes { > */ > enum wb_reason { > WB_REASON_BACKGROUND, > - WB_REASON_TRY_TO_FREE_PAGES, > + WB_REASON_VMSCAN, > WB_REASON_SYNC, > WB_REASON_PERIODIC, > WB_REASON_LAPTOP_TIMER, > diff --git a/include/trace/events/writeback.h > b/include/trace/events/writeback.h > index 2ccd9ccbf9ef..7bd8783a590f 100644 > --- a/include/trace/events/writeback.h > +++ b/include/trace/events/writeback.h > @@ -31,7 +31,7 @@ > > #define WB_WORK_REASON > \ > EM( WB_REASON_BACKGROUND, "background") \ > - EM( WB_REASON_TRY_TO_FREE_PAGES, "try_to_free_pages") \ > + EM( WB_REASON_VMSCAN, "vmscan") \ > EM( WB_REASON_SYNC, "sync") \ > EM( WB_REASON_PERIODIC, "periodic") \ > EM( WB_REASON_LAPTOP_TIMER, "laptop_timer") \ > 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 @@ static unsigned long do_try_to_free_pages(struct > zonelist *zonelist, > 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); > -- > 2.11.0 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to [email protected]. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> -- Michal Hocko SUSE Labs
