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authorMel Gorman <mgorman@techsingularity.net>2021-12-02 15:06:14 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2021-12-31 11:17:07 -0800
commit1b4e3f26f9f7553b260b8aed43967500961448a6 (patch)
tree5e5875dee79302caf399f3f01a40a3f1ba071ee4 /mm
parentf87bcc88f3028af584b0820bdf6e0e4cdc759d26 (diff)
downloadlinux-1b4e3f26f9f7553b260b8aed43967500961448a6.tar.bz2
mm: vmscan: Reduce throttling due to a failure to make progress
Mike Galbraith, Alexey Avramov and Darrick Wong all reported similar problems due to reclaim throttling for excessive lengths of time. In Alexey's case, a memory hog that should go OOM quickly stalls for several minutes before stalling. In Mike and Darrick's cases, a small memcg environment stalled excessively even though the system had enough memory overall. Commit 69392a403f49 ("mm/vmscan: throttle reclaim when no progress is being made") introduced the problem although commit a19594ca4a8b ("mm/vmscan: increase the timeout if page reclaim is not making progress") made it worse. Systems at or near an OOM state that cannot be recovered must reach OOM quickly and memcg should kill tasks if a memcg is near OOM. To address this, only stall for the first zone in the zonelist, reduce the timeout to 1 tick for VMSCAN_THROTTLE_NOPROGRESS and only stall if the scan control nr_reclaimed is 0, kswapd is still active and there were excessive pages pending for writeback. If kswapd has stopped reclaiming due to excessive failures, do not stall at all so that OOM triggers relatively quickly. Similarly, if an LRU is simply congested, only lightly throttle similar to NOPROGRESS. Alexey's original case was the most straight forward for i in {1..3}; do tail /dev/zero; done On vanilla 5.16-rc1, this test stalled heavily, after the patch the test completes in a few seconds similar to 5.15. Alexey's second test case added watching a youtube video while tail runs 10 times. On 5.15, playback only jitters slightly, 5.16-rc1 stalls a lot with lots of frames missing and numerous audio glitches. With this patch applies, the video plays similarly to 5.15. [lkp@intel.com: Fix W=1 build warning] Link: https://lore.kernel.org/r/99e779783d6c7fce96448a3402061b9dc1b3b602.camel@gmx.de Link: https://lore.kernel.org/r/20211124011954.7cab9bb4@mail.inbox.lv Link: https://lore.kernel.org/r/20211022144651.19914-1-mgorman@techsingularity.net Link: https://lore.kernel.org/r/20211202150614.22440-1-mgorman@techsingularity.net Link: https://linux-regtracking.leemhuis.info/regzbot/regression/20211124011954.7cab9bb4@mail.inbox.lv/ Reported-and-tested-by: Alexey Avramov <hakavlad@inbox.lv> Reported-and-tested-by: Mike Galbraith <efault@gmx.de> Reported-and-tested-by: Darrick J. Wong <djwong@kernel.org> Reported-by: kernel test robot <lkp@intel.com> Acked-by: Hugh Dickins <hughd@google.com> Tracked-by: Thorsten Leemhuis <regressions@leemhuis.info> Fixes: 69392a403f49 ("mm/vmscan: throttle reclaim when no progress is being made") Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmscan.c64
1 files changed, 55 insertions, 9 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fb9584641ac7..4c4d5f6cd8a3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1021,6 +1021,39 @@ static void handle_write_error(struct address_space *mapping,
unlock_page(page);
}
+static bool skip_throttle_noprogress(pg_data_t *pgdat)
+{
+ int reclaimable = 0, write_pending = 0;
+ int i;
+
+ /*
+ * If kswapd is disabled, reschedule if necessary but do not
+ * throttle as the system is likely near OOM.
+ */
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
+ return true;
+
+ /*
+ * If there are a lot of dirty/writeback pages then do not
+ * throttle as throttling will occur when the pages cycle
+ * towards the end of the LRU if still under writeback.
+ */
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ reclaimable += zone_reclaimable_pages(zone);
+ write_pending += zone_page_state_snapshot(zone,
+ NR_ZONE_WRITE_PENDING);
+ }
+ if (2 * write_pending <= reclaimable)
+ return true;
+
+ return false;
+}
+
void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
{
wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
@@ -1056,8 +1089,16 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
}
break;
+ case VMSCAN_THROTTLE_CONGESTED:
+ fallthrough;
case VMSCAN_THROTTLE_NOPROGRESS:
- timeout = HZ/2;
+ if (skip_throttle_noprogress(pgdat)) {
+ cond_resched();
+ return;
+ }
+
+ timeout = 1;
+
break;
case VMSCAN_THROTTLE_ISOLATED:
timeout = HZ/50;
@@ -3321,7 +3362,7 @@ again:
if (!current_is_kswapd() && current_may_throttle() &&
!sc->hibernation_mode &&
test_bit(LRUVEC_CONGESTED, &target_lruvec->flags))
- reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
sc))
@@ -3386,16 +3427,16 @@ static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
}
/*
- * Do not throttle kswapd on NOPROGRESS as it will throttle on
- * VMSCAN_THROTTLE_WRITEBACK if there are too many pages under
- * writeback and marked for immediate reclaim at the tail of
- * the LRU.
+ * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
+ * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
+ * under writeback and marked for immediate reclaim at the tail of the
+ * LRU.
*/
- if (current_is_kswapd())
+ if (current_is_kswapd() || cgroup_reclaim(sc))
return;
/* Throttle if making no progress at high prioities. */
- if (sc->priority < DEF_PRIORITY - 2)
+ if (sc->priority == 1 && !sc->nr_reclaimed)
reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
}
@@ -3415,6 +3456,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
unsigned long nr_soft_scanned;
gfp_t orig_mask;
pg_data_t *last_pgdat = NULL;
+ pg_data_t *first_pgdat = NULL;
/*
* If the number of buffer_heads in the machine exceeds the maximum
@@ -3478,14 +3520,18 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
/* need some check for avoid more shrink_zone() */
}
+ if (!first_pgdat)
+ first_pgdat = zone->zone_pgdat;
+
/* See comment about same check for global reclaim above */
if (zone->zone_pgdat == last_pgdat)
continue;
last_pgdat = zone->zone_pgdat;
shrink_node(zone->zone_pgdat, sc);
- consider_reclaim_throttle(zone->zone_pgdat, sc);
}
+ consider_reclaim_throttle(first_pgdat, sc);
+
/*
* Restore to original mask to avoid the impact on the caller if we
* promoted it to __GFP_HIGHMEM.