Michal Hocko <mhocko@xxxxxxxxxx> wrote: > On Fri 29-06-18 11:59:04, Greg Thelen wrote: >> Michal Hocko <mhocko@xxxxxxxxxx> wrote: >> >> > On Thu 28-06-18 16:19:07, Greg Thelen wrote: >> >> Michal Hocko <mhocko@xxxxxxxxxx> wrote: >> > [...] >> >> > + if (mem_cgroup_out_of_memory(memcg, mask, order)) >> >> > + return OOM_SUCCESS; >> >> > + >> >> > + WARN(1,"Memory cgroup charge failed because of no reclaimable memory! " >> >> > + "This looks like a misconfiguration or a kernel bug."); >> >> >> >> I'm not sure here if the warning should here or so strongly worded. It >> >> seems like the current task could be oom reaped with MMF_OOM_SKIP and >> >> thus mem_cgroup_out_of_memory() will return false. So there's nothing >> >> alarming in that case. >> > >> > If the task is reaped then its charges should be released as well and >> > that means that we should get below the limit. Sure there is some room >> > for races but this should be still unlikely. Maybe I am just >> > underestimating though. >> > >> > What would you suggest instead? >> >> I suggest checking MMF_OOM_SKIP or deleting the warning. > > So what do you do when you have MMF_OOM_SKIP task? Do not warn? Checking > for all the tasks would be quite expensive and remembering that from the > task selection not nice either. Why do you think it would help much? I assume we could just check current's MMF_OOM_SKIP - no need to check all tasks. My only (minor) objection is that the warning text suggests misconfiguration or kernel bug, when there may be neither. > I feel strongly that we have to warn when bypassing the charge limit > during the corner case because it can lead to unexpected behavior and > users should be aware of this fact. I am open to the wording or some > optimizations. I would prefer the latter on top with a clear description > how it helped in a particular case though. I would rather not over > optimize now without any story to back it. I'm fine with the warning. I know enough to look at dmesg logs to take an educates that the race occurred. We can refine it later if/when the reports start rolling in. No change needed.
