Messages in this thread | | | Date | Fri, 26 Aug 2011 11:35:01 +0400 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH] oom: skip frozen tasks |
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David Rientjes wrote: > On Thu, 25 Aug 2011, Michal Hocko wrote: > >>>>> That's obviously false since we call oom_killer_disable() in >>>>> freeze_processes() to disable the oom killer from ever being called in the >>>>> first place, so this is something you need to resolve with Rafael before >>>>> you cause more machines to panic. >>>> >>>> I didn't mean suspend/resume path (that is protected by oom_killer_disabled) >>>> so the patch doesn't make any change. >>> >>> Confused... freeze_processes() does try_to_freeze_tasks() before >>> oom_killer_disable() ? >> >> Yes you are right, I must have been blind. >> >> Now I see the point. We do not want to panic while we are suspending and >> the memory is really low just because all the userspace is already in >> the the fridge. >> Sorry for confusion. >> >> I still do not follow the oom_killer_disable note from David, though. >> > > oom_killer_disable() was added to that path for a reason when all threads > are frozen: memory allocations still occur in the suspend path in an oom > condition and adding the oom_killer_disable() will cause those > allocations to fail rather than sending pointless SIGKILLs to frozen > threads. > > Now consider if the only _eligible_ threads for oom kill (because of > cpusets or mempolicies) are those that are frozen. We certainly do not > want to panic because other cpusets are still getting work done. We'd > either want to add a mem to the cpuset or thaw the processes because the > cpuset is oom. > > You can't just selectively skip certain threads when their state can be > temporary without risking a panic. That's why this patch is a > non-starter. > > A much better solution would be to lower the badness score that the oom > killer uses for PF_FROZEN threads so that they aren't considered a > priority for kill unless there's nothing else left to kill.
Anyway, oom killer shouldn't loop endlessly if it see TIF_MEMDIE on frozen task, it must go on and try to kill somebody else. We cannot wait for thawing this task.
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