The commit is pushed to "branch-rh7-3.10.0-693.11.6.vz7.42.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.6.vz7.42.4
------>
commit 6254b06fdfb6656bd5f503a4bfc9d42db67e248d
Author: Andrey Ryabinin <aryabi...@virtuozzo.com>
Date: Wed Jan 31 18:29:34 2018 +0300
mm/vmscan: Use per-zone sum of reclaim_stat to change zone state.
Currently we collect reclaim stats per-lru list and set zone
flags based on these stats. This seems wrong, as lrus a per-memcg
thus one zone could have hundreds of them.
Move all that zone-related logic from shrink_inactive_list() to
shrink_zone, and make decisions based on per-zone sum of reclaim stat
instead of just per-lru.
https://jira.sw.ru/browse/PSBM-61409
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
---
mm/vmscan.c | 109 ++++++++++++++++++++++++++++++------------------------------
1 file changed, 54 insertions(+), 55 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e6dde1e15a54..d71fa15a1750 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1628,61 +1628,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct
lruvec *lruvec,
sc->stat->nr_immediate += stat.nr_immediate;
}
- /*
- * If reclaim is isolating dirty pages under writeback, it implies
- * that the long-lived page allocation rate is exceeding the page
- * laundering rate. Either the global limits are not being effective
- * at throttling processes due to the page distribution throughout
- * zones or there is heavy usage of a slow backing device. The
- * only option is to throttle from reclaim context which is not ideal
- * as there is no guarantee the dirtying process is throttled in the
- * same way balance_dirty_pages() manages.
- *
- * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
- * of pages under pages flagged for immediate reclaim and stall if any
- * are encountered in the nr_immediate check below.
- */
- if (stat.nr_writeback && stat.nr_writeback == nr_taken)
- zone_set_flag(zone, ZONE_WRITEBACK);
-
- if (!global_reclaim(sc) && stat.nr_immediate)
- congestion_wait(BLK_RW_ASYNC, HZ/10);
-
- if (sane_reclaim(sc)) {
- /*
- * Tag a zone as congested if all the dirty pages scanned were
- * backed by a congested BDI and wait_iff_congested will stall.
- */
- if (stat.nr_dirty && stat.nr_dirty == stat.nr_congested)
- zone_set_flag(zone, ZONE_CONGESTED);
-
- /*
- * If dirty pages are scanned that are not queued for IO, it
- * implies that flushers are not keeping up. In this case, flag
- * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
- * pages from reclaim context.
- */
- if (stat.nr_unqueued_dirty == nr_taken)
- zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
-
- /*
- * If kswapd scans pages marked marked for immediate
- * reclaim and under writeback (nr_immediate), it implies
- * that pages are cycling through the LRU faster than
- * they are written so also forcibly stall.
- */
- if (stat.nr_immediate)
- congestion_wait(BLK_RW_ASYNC, HZ/10);
- }
-
- /*
- * Stall direct reclaim for IO completions if underlying BDIs or zone
- * is congested. Allow kswapd to continue until it starts encountering
- * unqueued dirty pages or cycling through the LRU too quickly.
- */
- if (!sc->hibernation_mode && !current_is_kswapd())
- wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
-
trace_mm_vmscan_lru_shrink_inactive(zone_to_nid(zone), zone_idx(zone),
nr_scanned, nr_reclaimed,
stat.nr_dirty, stat.nr_writeback,
@@ -2485,6 +2430,60 @@ static void shrink_zone(struct zone *zone, struct
scan_control *sc,
shrink_slab(slab_gfp, zone_to_nid(zone), NULL,
sc->priority, false);
+ if (global_reclaim(sc)) {
+ /*
+ * If reclaim is isolating dirty pages under writeback,
it implies
+ * that the long-lived page allocation rate is
exceeding the page
+ * laundering rate. Either the global limits are not
being effective
+ * at throttling processes due to the page distribution
throughout
+ * zones or there is heavy usage of a slow backing
device. The
+ * only option is to throttle from reclaim context
which is not ideal
+ * as there is no guarantee the dirtying process is
throttled in the
+ * same way balance_dirty_pages() manages.
+ *
+ * Once a zone is flagged ZONE_WRITEBACK, kswapd will
count the number
+ * of pages under pages flagged for immediate reclaim
and stall if any
+ * are encountered in the nr_immediate check below.
+ */
+ if (stat.nr_writeback && stat.nr_writeback ==
stat.nr_taken)
+ zone_set_flag(zone, ZONE_WRITEBACK);
+
+ /*
+ * Tag a zone as congested if all the dirty pages
scanned were
+ * backed by a congested BDI and wait_iff_congested
will stall.
+ */
+ if (stat.nr_dirty && stat.nr_dirty == stat.nr_congested)
+ zone_set_flag(zone, ZONE_CONGESTED);
+ /*
+ * If dirty pages are scanned that are not queued for
IO, it
+ * implies that flushers are not keeping up. In this
case, flag
+ * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start
writing
+ * pages from reclaim context.
+ */
+ if (stat.nr_unqueued_dirty == stat.nr_taken)
+ zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
+
+ /*
+ * If kswapd scans pages marked marked for immediate
+ * reclaim and under writeback (nr_immediate), it
implies
+ * that pages are cycling through the LRU faster than
+ * they are written so also forcibly stall.
+ */
+ if (stat.nr_immediate)
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+ }
+
+ if (!global_reclaim(sc) && stat.nr_immediate)
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+ /*
+ * Stall direct reclaim for IO completions if underlying BDIs
or zone
+ * is congested. Allow kswapd to continue until it starts
encountering
+ * unqueued dirty pages or cycling through the LRU too quickly.
+ */
+ if (!sc->hibernation_mode && !current_is_kswapd())
+ wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
+
if (reclaim_state) {
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
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