diff options
| author | Michal Hocko | 2016-12-02 17:26:48 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2016-12-02 18:48:03 -0800 |
| commit | bd041733c9f612b66c519e5a8b1a98b05b94ed24 (patch) | |
| tree | 38be7a4d2b223f3b7091fc989191bee25ed29bf9 /mm/vmscan.c | |
| parent | 20ab67a563f5299c09a234164c372aba5a59add8 (diff) | |
mm, vmscan: add cond_resched() into shrink_node_memcg()
Boris Zhmurov has reported RCU stalls during the kswapd reclaim:
INFO: rcu_sched detected stalls on CPUs/tasks:
23-...: (22 ticks this GP) idle=92f/140000000000000/0 softirq=2638404/2638404 fqs=23
(detected by 4, t=6389 jiffies, g=786259, c=786258, q=42115)
Task dump for CPU 23:
kswapd1 R running task 0 148 2 0x00000008
Call Trace:
shrink_node+0xd2/0x2f0
kswapd+0x2cb/0x6a0
mem_cgroup_shrink_node+0x160/0x160
kthread+0xbd/0xe0
__switch_to+0x1fa/0x5c0
ret_from_fork+0x1f/0x40
kthread_create_on_node+0x180/0x180
a closer code inspection has shown that we might indeed miss all the
scheduling points in the reclaim path if no pages can be isolated from
the LRU list. This is a pathological case but other reports from Donald
Buczek have shown that we might indeed hit such a path:
clusterd-989 [009] .... 118023.654491: mm_vmscan_direct_reclaim_end: nr_reclaimed=193
kswapd1-86 [001] dN.. 118023.987475: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239830 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118024.320968: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239844 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118024.654375: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239858 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118024.987036: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239872 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118025.319651: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239886 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118025.652248: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239900 nr_taken=0 file=1
kswapd1-86 [001] dN.. 118025.984870: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239914 nr_taken=0 file=1
[...]
kswapd1-86 [001] dN.. 118084.274403: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4241133 nr_taken=0 file=1
this is minute long snapshot which didn't take a single page from the
LRU. It is not entirely clear why only 1303 pages have been scanned
during that time (maybe there was a heavy IRQ activity interfering).
In any case it looks like we can really hit long periods without
scheduling on non preemptive kernels so an explicit cond_resched() in
shrink_node_memcg which is independent on the reclaim operation is due.
Link: http://lkml.kernel.org/r/20161202095841.16648-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Boris Zhmurov <bb@kernelpanic.ru>
Tested-by: Boris Zhmurov <bb@kernelpanic.ru>
Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Reported-by: "Christopher S. Aker" <caker@theshore.net>
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
| -rw-r--r-- | mm/vmscan.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 76fda2268148..d75cdf360730 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2354,6 +2354,8 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc } } + cond_resched(); + if (nr_reclaimed < nr_to_reclaim || scan_adjusted) continue; |