On 6/19/2012 2:26 AM, David Rientjes wrote: > On Tue, 19 Jun 2012, KOSAKI Motohiro wrote: > >>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c >>> --- a/mm/oom_kill.c >>> +++ b/mm/oom_kill.c >>> @@ -746,10 +746,11 @@ out: >>> read_unlock(&tasklist_lock); >>> >>> /* >>> - * Give "p" a good chance of killing itself before we >>> + * Give "p" a good chance of exiting before we >>> * retry to allocate memory unless "p" is current >>> */ >>> - if (killed && !test_thread_flag(TIF_MEMDIE)) >>> + if (killed && !fatal_signal_pending(current) && >>> + !(current->flags & PF_EXITING)) >>> schedule_timeout_uninterruptible(1); >>> } >> >> Why don't check gfp_flags? I think the rule is, >> >> 1) a thread of newly marked as TIF_MEMDIE >> -> now it has a capability to access reseve memory. let's immediately retry. >> 2) allocation for GFP_HIGHUSER_MOVABLE >> -> we can fail to allocate it safely. let's immediately fail. >> (I suspect we need to change page allocator too) >> 3) GFP_KERNEL and PF_EXITING >> -> don't retry immediately. It shall fail again. let's wait until >> killed process >> is exited. >> > > The killed process may exit but it does not guarantee that its memory will > be freed if it's shared with current. This is the case that the patch is > addressing, where right now we unnecessarily schedule if current has been > killed or is already along the exit path. We want to retry as soon as > possible so that either the allocation now succeeds or we can recall the > oom killer as soon as possible and get TIF_MEMDIE set because we have a > fatal signal so current may exit in a timely way as well. The point is > that if current has either a SIGKILL or is already exiting as it returns > from the oom killer, it does no good to continue to stall and prevent that > memory freeing. You missed live lock risk. immediate retry makes immediate fail if no one freed any memory. Even if the task call out_of_memory() again, select_bad_process() may return -1 and don't makes any forward progress. -- 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>