The patch titled
Subject: mm: fix condition for throttle_direct_reclaim
has been added to the -mm tree. Its filename is
mm-fix-100%-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-100%25-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-100%25-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Shakeel Butt <shakeelb@xxxxxxxxxx>
Subject: mm: fix condition for throttle_direct_reclaim
Since "mm: fix 100% CPU kswapd busyloop on unreclaimable nodes" kswapd has
been modified to give up after MAX_RECLAIM_RETRIES number of unsucessful
iterations. Before going to sleep, kswapd thread will unconditionally
wakeup all threads sleeping on pfmemalloc_wait. However the awoken
threads will recheck the watermarks and wake the kswapd thread and sleep
again on pfmemalloc_wait. There is a chance that the system might end up
in livelock between unsuccessful kswapd and direct reclaimers because all
direct reclaimer might end up in throttle_direct_reclaim and there is
nobody to make a forward progress. So, add kswapd_failures check on the
throttle_direct_reclaim condition.
Link: http://lkml.kernel.org/r/20170314183228.20152-1-shakeelb@xxxxxxxxxx
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff -puN mm/vmscan.c~mm-fix-100%-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2 mm/vmscan.c
--- a/mm/vmscan.c~mm-fix-100%-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2
+++ a/mm/vmscan.c
@@ -2822,7 +2822,7 @@ retry:
return 0;
}
-static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
+static bool allow_direct_reclaim(pg_data_t *pgdat)
{
struct zone *zone;
unsigned long pfmemalloc_reserve = 0;
@@ -2830,6 +2830,9 @@ static bool pfmemalloc_watermark_ok(pg_d
int i;
bool wmark_ok;
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
+ return true;
+
for (i = 0; i <= ZONE_NORMAL; i++) {
zone = &pgdat->node_zones[i];
if (!managed_zone(zone) ||
@@ -2910,7 +2913,7 @@ static bool throttle_direct_reclaim(gfp_
/* Throttle based on the first usable node */
pgdat = zone->zone_pgdat;
- if (pfmemalloc_watermark_ok(pgdat))
+ if (allow_direct_reclaim(pgdat))
goto out;
break;
}
@@ -2932,14 +2935,14 @@ static bool throttle_direct_reclaim(gfp_
*/
if (!(gfp_mask & __GFP_FS)) {
wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
- pfmemalloc_watermark_ok(pgdat), HZ);
+ allow_direct_reclaim(pgdat), HZ);
goto check_pending;
}
/* Throttle until kswapd wakes the process */
wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
- pfmemalloc_watermark_ok(pgdat));
+ allow_direct_reclaim(pgdat));
check_pending:
if (fatal_signal_pending(current))
@@ -3119,7 +3122,7 @@ static bool prepare_kswapd_sleep(pg_data
/*
* The throttled processes are normally woken up in balance_pgdat() as
- * soon as pfmemalloc_watermark_ok() is true. But there is a potential
+ * soon as allow_direct_reclaim() is true. But there is a potential
* race between when kswapd checks the watermarks and a process gets
* throttled. There is also a potential race if processes get
* throttled, kswapd wakes, a large process exits thereby balancing the
@@ -3304,7 +3307,7 @@ static int balance_pgdat(pg_data_t *pgda
* able to safely make forward progress. Wake them
*/
if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
- pfmemalloc_watermark_ok(pgdat))
+ allow_direct_reclaim(pgdat))
wake_up_all(&pgdat->pfmemalloc_wait);
/* Check if kswapd should be suspending */
_
Patches currently in -mm which might be from shakeelb@xxxxxxxxxx are
mm-fix-100%-cpu-kswapd-busyloop-on-unreclaimable-nodes-fix-2.patch
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