The patch titled mm: vmscan: do not apply pressure to slab if we are not applying pressure to zone has been added to the -mm tree. Its filename is mm-vmscan-do-not-apply-pressure-to-slab-if-we-are-not-applying-pressure-to-zone.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: mm: vmscan: do not apply pressure to slab if we are not applying pressure to zone From: Mel Gorman <mgorman@xxxxxxx> During allocator-intensive workloads, kswapd will be woken frequently causing free memory to oscillate between the high and min watermark. This is expected behaviour. When kswapd applies pressure to zones during node balancing, it checks if the zone is above a high+balance_gap threshold. If it is, it does not apply pressure but it unconditionally shrinks slab on a global basis which is excessive. In the event kswapd is being kept awake due to a high small unreclaimable zone, it skips zone shrinking but still calls shrink_slab(). Once pressure has been applied, the check for zone being unreclaimable is being made before the check is made if all_unreclaimable should be set. This miss of unreclaimable can cause has_under_min_watermark_zone to be set due to an unreclaimable zone preventing kswapd backing off on congestion_wait(). Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reported-by: Pádraig Brady <P@xxxxxxxxxxxxxx> Tested-by: Pádraig Brady <P@xxxxxxxxxxxxxx> Tested-by: Andrew Lutomirski <luto@xxxxxxx> Acked-by: Rik van Riel <riel@xxxxxxxxxx> Cc: Minchan Kim <minchan.kim@xxxxxxxxx> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff -puN mm/vmscan.c~mm-vmscan-do-not-apply-pressure-to-slab-if-we-are-not-applying-pressure-to-zone mm/vmscan.c --- a/mm/vmscan.c~mm-vmscan-do-not-apply-pressure-to-slab-if-we-are-not-applying-pressure-to-zone +++ a/mm/vmscan.c @@ -2510,18 +2510,18 @@ loop_again: KSWAPD_ZONE_BALANCE_GAP_RATIO); if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) + balance_gap, - end_zone, 0)) + end_zone, 0)) { shrink_zone(priority, zone, &sc); - reclaim_state->reclaimed_slab = 0; - nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); - sc.nr_reclaimed += reclaim_state->reclaimed_slab; - total_scanned += sc.nr_scanned; - if (zone->all_unreclaimable) - continue; - if (nr_slab == 0 && - !zone_reclaimable(zone)) - zone->all_unreclaimable = 1; + reclaim_state->reclaimed_slab = 0; + nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); + sc.nr_reclaimed += reclaim_state->reclaimed_slab; + total_scanned += sc.nr_scanned; + + if (nr_slab == 0 && !zone_reclaimable(zone)) + zone->all_unreclaimable = 1; + } + /* * If we've done a decent amount of scanning and * the reclaim ratio is low, start doing writepage @@ -2531,6 +2531,9 @@ loop_again: total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) sc.may_writepage = 1; + if (zone->all_unreclaimable) + continue; + if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), end_zone, 0)) { all_zones_ok = 0; _ Patches currently in -mm which might be from mgorman@xxxxxxx are mm-vmscan-correct-check-for-kswapd-sleeping-in-sleeping_prematurely.patch mm-vmscan-do-not-apply-pressure-to-slab-if-we-are-not-applying-pressure-to-zone.patch mm-vmscan-evaluate-the-watermarks-against-the-correct-classzone.patch mm-vmscan-only-read-new_classzone_idx-from-pgdat-when-reclaiming-successfully.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html