Re: [patch] memcg: add oom killer delay

[David Rientjes <rientjes@google.com>]

On Tue, 15 Feb 2011, David Rientjes wrote:

> > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> 
> Thanks!
> 
> > Hm. But I'm not sure how this will be used.
> > 
> 
> Since this patch hasn't been added to -mm even with your acked-by, I'm 
> assuming Andrew is waiting for an answer to this :)  I thought it was 
> fairly well covered in the changelog, but I'll elaborate:
> 
> We can already give userspace a grace period to act before oom killing a 
> task by utilizing memory.oom_control.  That's not what the oom killer 
> delay addresses, however.  This addresses a very specific (and real) 
> problem that occurs when userspace wants that grace period but is unable 
> to respond, for whatever reason, to either increase the hard limit or 
> allow the oom kill to proceed.  The possibility of that happening would 
> cause that memcg to livelock because no forward progress could be made 
> when oom, which is a negative result.  We don't have that possibility with 
> the global oom killer since the kernel will always choose to act if memory 
> freeing is not imminent: in other words, since we've opened the window for 
> livelock because of an unreliable userspace via a kernel feature -- namely 
> memory.oom_control -- then it's only responsible to provide an alternate 
> means to configure the cgroup for the same grace period without risking 
> livelock.
> 

Andrew, can this be merged in -mm?

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