On Tue 16-07-19 15:21:17, Qian Cai wrote: [...] > Thanks to this commit, there are allocation with __GFP_DIRECT_RECLAIM that > succeeded would keep trying with __GFP_NOFAIL for kmemleak tracking object > allocations. Well, not really. Because low order allocations with __GFP_DIRECT_RECLAIM basically never fail (they keep retrying) even without GFP_NOFAIL because that flag is actually to guarantee no failure. And for high order allocations the nofail mode is actively harmful. It completely changes the behavior of a system. A light costly order workload could put the system on knees and completely change the behavior. I am not really convinced this is a good behavior of a debugging feature TBH. > Otherwise, one kmemleak object allocation failure would kill the > whole kmemleak. Which is not great but quite likely a better than an unpredictable MM behavior caused by NOFAIL storms. Really, this NOFAIL patch is a completely broken behavior. There shouldn't be much discussion about reverting it. I would even argue it shouldn't have been merged in the first place. It doesn't have any acks nor reviewed-bys while it abuses __GFP_NOFAIL which is generally discouraged to be used. Thanks! -- Michal Hocko SUSE Labs
