On 10/22/2012 04:51 PM, Michal Hocko wrote: > [Sorry for the late reply] > > On Mon 22-10-12 16:34:15, Glauber Costa wrote: >> 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 ? > > Yes it makes sense to be consistent with the global case. While we are > at it, do we need to consider PF_DUMPCORE resp. !__GFP_NOFAIL? > at least from kmem, GFP_NOFAIL will not reach this codepath. We will ditch it to the root in memcontrol.h -- 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>