Michal Hocko wrote: > From: Michal Hocko <mhocko@xxxxxxxx> > > __alloc_pages_may_oom is the central place to decide when the > out_of_memory should be invoked. This is a good approach for most checks > there because they are page allocator specific and the allocation fails > right after. > > The notable exception is GFP_NOFS context which is faking > did_some_progress and keep the page allocator looping even though there > couldn't have been any progress from the OOM killer. This patch doesn't > change this behavior because we are not ready to allow those allocation > requests to fail yet. Instead __GFP_FS check is moved down to > out_of_memory and prevent from OOM victim selection there. There are > two reasons for that > - OOM notifiers might release some memory even from this context > as none of the registered notifier seems to be FS related > - this might help a dying thread to get an access to memory > reserves and move on which will make the behavior more > consistent with the case when the task gets killed from a > different context. Allowing !__GFP_FS allocations to get TIF_MEMDIE by calling the shortcuts in out_of_memory() would be fine. But I don't like the direction you want to go. I don't like failing !__GFP_FS allocations without selecting OOM victim ( http://lkml.kernel.org/r/201603252054.ADH30264.OJQFFLMOHFSOVt@xxxxxxxxxxxxxxxxxxx ). Also, I suggested removing all shortcuts by setting TIF_MEMDIE from oom_kill_process() ( http://lkml.kernel.org/r/1458529634-5951-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx ). > > Keep a comment in __alloc_pages_may_oom to make sure we do not forget > how GFP_NOFS is special and that we really want to do something about > it. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > --- > > Hi, > I am sending this as an RFC now even though I think this makes more > sense than what we have right now. Maybe there are some side effects > I do not see, though. A more tricky part is the OOM notifier part > becasue future notifiers might decide to depend on the FS and we can > lockup. Is this something to worry about, though? Would such a notifier > be correct at all? I would call it broken as it would put OOM killer out > of the way on the contended system which is a plain bug IMHO. > > If this looks like a reasonable approach I would go on think about how > we can extend this for the oom_reaper and queue the current thread for > the reaper to free some of the memory. > > Any thoughts -- 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>