David Rientjes wrote: > > By the way, will you share the reproducer (and how to use the reproducer) ? > > > > On an UP kernel with swap disabled, you limit a memcg to 100MB and start > three processes that each fault 40MB attached to it. Same reproducer as > the "mm, oom: make a last minute check to prevent unnecessary memcg oom > kills" patch except in that case there are two cores. > I'm not a heavy memcg user. Please provide steps for reproducing your problem in a "copy and pastable" way (e.g. bash script, C program). > > @@ -1576,6 +1576,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, > > */ > > ret = should_force_charge() || out_of_memory(&oc); > > mutex_unlock(&oom_lock); > > + schedule_timeout_killable(1); > > return ret; > > } > > > > If current was process chosen for oom kill, this would actually induce the > problem, not fix it. > Why? Memcg OOM path allows using forced charge path if should_force_charge() == true. Since your lockup report Call Trace: shrink_node+0x40d/0x7d0 do_try_to_free_pages+0x13f/0x470 try_to_free_mem_cgroup_pages+0x16d/0x230 try_charge+0x247/0xac0 mem_cgroup_try_charge+0x10a/0x220 mem_cgroup_try_charge_delay+0x1e/0x40 handle_mm_fault+0xdf2/0x15f0 do_user_addr_fault+0x21f/0x420 page_fault+0x2f/0x40 says that allocating thread was calling try_to_free_mem_cgroup_pages() from try_charge(), allocating thread must be able to reach mem_cgroup_out_of_memory() from mem_cgroup_oom() from try_charge(). And actually Memory cgroup out of memory: Killed process 808 (repro) total-vm:41944kB, anon-rss:35344kB, file-rss:504kB, shmem-rss:0kB, UID:0 pgtables:108kB oom_score_adj:0 says that allocating thread did reach mem_cgroup_out_of_memory(). Then, allocating thread must be able to sleep at mem_cgroup_out_of_memory() if schedule_timeout_killable(1) is mem_cgroup_out_of_memory(). Also, if current process was chosen for OOM-kill, current process will be able to leave try_charge() due to should_force_charge() == true, won't it? Thus, how can "this would actually induce the problem, not fix it." happen? If your problem is that something keeps allocating threads away from reaching should_force_charge() check, please explain the mechanism. If that is explained, I would agree that schedule_timeout_killable(1) in mem_cgroup_out_of_memory() won't help.
