| Message ID | 1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] mm: memcg: Fix memcg reclaim soft lockup | expand |
On Thu, Aug 27, 2020 at 10:32:29AM +0800, Xunlei Pang wrote: > We've met softlockup with "CONFIG_PREEMPT_NONE=y", when > the target memcg doesn't have any reclaimable memory. > > It can be easily reproduced as below: > watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204] > CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12 > Call Trace: > shrink_lruvec+0x49f/0x640 > shrink_node+0x2a6/0x6f0 > do_try_to_free_pages+0xe9/0x3e0 > try_to_free_mem_cgroup_pages+0xef/0x1f0 > try_charge+0x2c1/0x750 > mem_cgroup_charge+0xd7/0x240 > __add_to_page_cache_locked+0x2fd/0x370 > add_to_page_cache_lru+0x4a/0xc0 > pagecache_get_page+0x10b/0x2f0 > filemap_fault+0x661/0xad0 > ext4_filemap_fault+0x2c/0x40 > __do_fault+0x4d/0xf9 > handle_mm_fault+0x1080/0x1790 > > It only happens on our 1-vcpu instances, because there's no chance > for oom reaper to run to reclaim the to-be-killed process. > > Add a cond_resched() at the upper shrink_node_memcgs() to solve this > issue, this will mean that we will get a scheduling point for each > memcg in the reclaimed hierarchy without any dependency on the > reclaimable memory in that memcg thus making it more predictable. > > Acked-by: Chris Down <chris@chrisdown.name> > Acked-by: Michal Hocko <mhocko@suse.com> > Suggested-by: Michal Hocko <mhocko@suse.com> > Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c index 99e1796..9727dd8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2615,6 +2615,14 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) unsigned long reclaimed; unsigned long scanned; + /* + * This loop can become CPU-bound when target memcgs + * aren't eligible for reclaim - either because they + * don't have any reclaimable pages, or because their + * memory is explicitly protected. Avoid soft lockups. + */ + cond_resched(); + mem_cgroup_calculate_protection(target_memcg, memcg); if (mem_cgroup_below_min(memcg)) {