On Wednesday, January 25, 2017 4:00 PM Michal Hocko wrote: > On Wed 25-01-17 15:00:51, Hillf Danton wrote: > > On Tuesday, January 24, 2017 8:41 PM Michal Hocko wrote: > > > On Fri 20-01-17 16:33:36, Hillf Danton wrote: > > > > > > > > On Tuesday, December 20, 2016 9:49 PM Michal Hocko wrote: > > > > > > > > > > @@ -1013,7 +1013,7 @@ bool out_of_memory(struct oom_control *oc) > > > > > * make sure exclude 0 mask - all other users should have at least > > > > > * ___GFP_DIRECT_RECLAIM to get here. > > > > > */ > > > > > - if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL))) > > > > > + if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS)) > > > > > return true; > > > > > > > > > As to GFP_NOFS|__GFP_NOFAIL request, can we check gfp mask > > > > one bit after another? > > > > > > > > if (oc->gfp_mask) { > > > > if (!(oc->gfp_mask & __GFP_FS)) > > > > return false; > > > > > > > > /* No service for request that can handle fail result itself */ > > > > if (!(oc->gfp_mask & __GFP_NOFAIL)) > > > > return false; > > > > } > > > > > > I really do not understand this request. > > > > It's a request of both NOFS and NOFAIL, and I think we can keep it from > > hitting oom killer by shuffling the current gfp checks. > > I hope it can make nit sense to your work. > > > > I still do not understand. The whole point we are doing the late > __GFP_FS check is explained in 3da88fb3bacf ("mm, oom: move GFP_NOFS > check to out_of_memory"). And the reason why I am _removing_ > __GFP_NOFAIL is explained in the changelog of this patch. > > > > This patch is removing the __GFP_NOFAIL part... > > > > Yes, and I don't stick to handling NOFAIL requests inside oom. > > > > > Besides that why should they return false? > > > > It's feedback to page allocator that no kill is issued, and > > extra attention is needed. > > Be careful, the semantic of out_of_memory is different. Returning false > means that the oom killer has been disabled and so the allocation should > fail rather than loop for ever. > By returning false, I mean that oom killer is making no progress. And I prefer to give up looping if oom killer can't help. It's a change in the current semantic to fail the request and I have to test it isn't bad. thanks Hillf -- 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>