On Tue 29-03-16 22:45:40, Tetsuo Handa wrote: > Michal Hocko wrote: > > From: Michal Hocko <[email protected]> > > > > __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/[email protected] > ).
I didn't get to read and digest that email yet but from a quick glance it doesn't seem to be directly related to this patch. Even if we decide that __GFP_FS vs. OOM killer logic is flawed for some reason then would build on top as granting the access to memory reserves is not against it. > 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-ker...@i-love.sakura.ne.jp > ). I personally do not like this much. I believe we have already tried to explain why we have (some of) those shortcuts. They might be too optimistic and there is a room for improvements for sure but I am not convinced we can get rid of them that easily. -- Michal Hocko SUSE Labs
