The patch titled
vmscan: fix a livelock in kswapd
has been added to the -mm tree. Its filename is
vmscan-fix-a-livelock-in-kswapd.patch
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Subject: vmscan: fix a livelock in kswapd
From: Shaohua Li <shaohua...@intel.com>
I'm running a workload which triggers a lot of swap in a machine with 4 nodes.
After I kill the workload, I found a kswapd livelock. Sometimes kswapd3 or
kswapd2 are keeping running and I can't access filesystem, but most memory is
free.
This looks like a regression since commit 08951e545918c159 ("mm: vmscan:
correct check for kswapd sleeping in sleeping_prematurely").
Node 2 and 3 have only ZONE_NORMAL, but balance_pgdat() will return 0 for
classzone_idx. The reason is end_zone in balance_pgdat() is 0 by default,
if all zones have watermark ok, end_zone will keep 0.
Later sleeping_prematurely() always returns true. Because this is an
order 3 wakeup, and if classzone_idx is 0, both balanced_pages and
present_pages in pgdat_balanced() are 0. We add a special case here. If
a zone has no page, we think it's balanced. This fixes the livelock.
Signed-off-by: Shaohua Li <shaohua...@intel.com>
Acked-by: Mel Gorman <mgor...@suse.de>
Cc: Minchan Kim <minchan....@gmail.com>
Cc: <sta...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
---
mm/vmscan.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN mm/vmscan.c~vmscan-fix-a-livelock-in-kswapd mm/vmscan.c
--- a/mm/vmscan.c~vmscan-fix-a-livelock-in-kswapd
+++ a/mm/vmscan.c
@@ -2310,7 +2310,8 @@ static bool pgdat_balanced(pg_data_t *pg
for (i = 0; i <= classzone_idx; i++)
present_pages += pgdat->node_zones[i].present_pages;
- return balanced_pages > (present_pages >> 2);
+ /* A special case here: if zone has no page, we think it's balanced */
+ return balanced_pages >= (present_pages >> 2);
}
/* is kswapd sleeping prematurely? */
_
Patches currently in -mm which might be from shaohua...@intel.com are
vmscan-fix-a-livelock-in-kswapd.patch
linux-next.patch
acpi-add-missing-_osi-strings-resend.patch
tmpfs-simplify-prealloc_page.patch
intel_idle-fix-api-misuse.patch
intel_idle-disable-auto_demotion-for-hotplugged-cpus.patch
memcg-export-memory-cgroups-swappiness-with-mem_cgroup_swappiness.patch
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