On Fri 04-08-17 20:44:52, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Fri 04-08-17 20:10:09, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > > > On Thu 03-08-17 16:53:40, Tetsuo Handa wrote: > > > > > Michal Hocko wrote: > > > > > > > We don't need to give up task_will_free_mem(current) without trying > > > > > > > allocation from memory reserves. We will need to select next OOM victim > > > > > > > only when allocation from memory reserves did not help. > > > > > > > > > > > > > > Thus, this patch allows task_will_free_mem(current) to ignore MMF_OOM_SKIP > > > > > > > for once so that task_will_free_mem(current) will not start selecting next > > > > > > > OOM victim without trying allocation from memory reserves. > > > > > > > > > > > > As I've already said this is an ugly hack and once we have > > > > > > http://lkml.kernel.org/r/20170727090357.3205-2-mhocko@xxxxxxxxxx merged > > > > > > then it even shouldn't be needed because _all_ threads of the oom victim > > > > > > will have an instant access to memory reserves. > > > > > > > > > > > > So I do not think we want to merge this. > > > > > > > > > > > > > > > > No, we still want to merge this, for 4.8+ kernels which won't get your patch > > > > > backported will need this. Even after your patch is merged, there is a race > > > > > window where allocating threads are between after gfp_pfmemalloc_allowed() and > > > > > before mutex_trylock(&oom_lock) in __alloc_pages_may_oom() which means that > > > > > some threads could call out_of_memory() and hit this task_will_free_mem(current) > > > > > test. Ignoring MMF_OOM_SKIP for once is still useful. > > > > > > > > I disagree. I am _highly_ skeptical this is a stable material. The > > > > mentioned test case is artificial and the source of the problem is > > > > somewhere else. Moreover the culprit is somewhere else. It is in the oom > > > > reaper setting MMF_OOM_SKIP too early and it should be addressed there. > > > > Do not add workarounds where they are not appropriate. > > > > > > > So, what alternative can you provide us for now? > > > > As I've already said http://lkml.kernel.org/r/20170727090357.3205-2-mhocko@xxxxxxxxxx > > seems to be a better alternative. I am waiting for further review > > feedback before reposting it again. > > > As I've already said, your patch does not close this race completely. Neither this patch. > Your patch will be too drastic/risky for stable material. As I've said this doesn't look like a stable material. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
