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SubjectRe: [RFC][PATCH] memcg: page fault oom improvement
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-02-23 12:03:15]:

> Nishimura-san, could you review and test your extreme test case with this ?
>
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> 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@google.com>
> Cc: Balbir Singh <balbir@in.ibm.com>
> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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?
--
Three Cheers,
Balbir


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