On 10/20/2012 12:34 AM, David Rientjes wrote: > 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. > That seems reasonable to me. Michal ? -- 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>