On Tue, 23 Feb 2010 11:40:20 +0530 Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-02-23 12:03:15]: > > > Nishimura-san, could you review and test your extreme test case with this ? > > > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > Now, because of page_fault_oom_kill, returning VM_FAULT_OOM means > > random oom-killer should be called. Considering memcg, it handles > > OOM-kill in its own logic, there was a problem as "oom-killer called > > twice" problem. > > > > By commit a636b327f731143ccc544b966cfd8de6cb6d72c6, I added a check > > in pagefault_oom_killer shouldn't kill some (random) task if > > memcg's oom-killer already killed anyone. > > That was done by comapring current jiffies and last oom jiffies of memcg. > > > > I thought that easy fix was enough, but Nishimura could write a test case > > where checking jiffies is not enough. So, my fix was not enough. > > This is a fix of above commit. > > > > This new one does this. > > * memcg's try_charge() never returns -ENOMEM if oom-killer is allowed. > > * If someone is calling oom-killer, wait for it in try_charge(). > > * If TIF_MEMDIE is set as a result of try_charge(), return 0 and > > allow process to make progress (and die.) > > * removed hook in pagefault_out_of_memory. > > > > By this, pagefult_out_of_memory will be never called if memcg's oom-killer > > is called and scattered codes are now in memcg's charge logic again. > > > > TODO: > > If __GFP_WAIT is not specified in gfp_mask flag, VM_FAULT_OOM will return > > anyway. We need to investigate it whether there is a case. > > > > Cc: David Rientjes <rientjes@xxxxxxxxxx> > > Cc: Balbir Singh <balbir@xxxxxxxxxx> > > Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > I've not reviewed David's latest OOM killer changes. Are these changes based on top of > what is going to come in with David's proposal? About this change. no. This is an independent patch. But through these a few month work, I(we) noticed page_fault_out_of_memory() is dangerous and VM_FALUT_OOM should not be returned as much as possible. About memcg, it's not necessary to return VM_FAULT_OOM when we know oom-killer is called. This fix itself is straightforward. But difficult thing here is test case, I think. 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>