On Tue, 16 Feb 2010 18:28:05 -0800 (PST) David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Wed, 17 Feb 2010, KAMEZAWA Hiroyuki wrote: > > > > What do you think about making pagefaults use out_of_memory() directly and > > > respecting the sysctl_panic_on_oom settings? > > > > > > > I don't think this patch is good. Because several memcg can > > cause oom at the same time independently, system-wide oom locking is > > unsuitable. BTW, what I doubt is much more fundamental thing. > > > > We want to lock all populated zones with ZONE_OOM_LOCKED to avoid > needlessly killing more than one task regardless of how many memcgs are > oom. > Current implentation archive what memcg want. Why remove and destroy memcg ? > > What I doubt at most is "why VM_FAULT_OOM is necessary ? or why we have > > to call oom_killer when page fault returns it". > > Is there someone who returns VM_FAULT_OOM without calling page allocator > > and oom-killer helps something in such situation ? > > > > Before we invoked the oom killer for VM_FAULT_OOM, we simply sent a > SIGKILL to current because we simply don't have memory to fault the page > in, it's better to select a memory-hogging task to kill based on badness() > than to constantly kill current which may not help in the long term. > What I mean is - What VM_FAULT_OOM means is not "memory is exhausted" but "something is exhausted". For example, when hugepages are all used, it may return VM_FAULT_OOM. Especially when nr_overcommit_hugepage == usage_of_hugepage, it returns VM_FAULT_OOM. Then, what oom-killer can help it ? I think never and the requester should die. Before modifying current code, I think we have to check all VM_FAULT_OOM and distinguish - memory is exhausted (and page allocater wasn't called.) - something other than memory is exhausted. And, in hugepage case, even order > PAGE_ALLOC_COSTLY_ORDER, oom-killer is called and pagegault_oom_kill kills tasks randomly. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>