On Fri, 19 Oct 2012, Glauber Costa wrote: > >>> What about gfp & __GFP_FS? > >>> > >> > >> Do you intend to prevent or allow OOM under that flag? I personally > >> think that anything that accepts to be OOM-killed should have GFP_WAIT > >> set, so that ought to be enough. > >> > > > > The oom killer in the page allocator cannot trigger without __GFP_FS > > because direct reclaim has little chance of being very successful and > > thus we end up needlessly killing processes, and that tends to happen > > quite a bit if we dont check for it. Seems like this would also happen > > with memcg if mem_cgroup_reclaim() has a large probability of failing? > > > > I can indeed see tests for GFP_FS in some key locations in mm/ before > calling the OOM Killer. > > Should I test for GFP_IO as well? It's not really necessary, if __GFP_IO isn't set then it wouldn't make sense for __GFP_FS to be set. > If the idea is preventing OOM to > trigger for allocations that can write their pages back, how would you > feel about the following test: > > may_oom = (gfp & GFP_KERNEL) && !(gfp & __GFP_NORETRY) ? > I would simply copy the logic from the page allocator and only trigger oom for __GFP_FS and !__GFP_NORETRY. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
