linux-kernel - Re: [PATCH] trace: Set oom_score_adj to maximum for ring buffer allocating process

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Message-ID: <alpine.DEB.2.00.1105261315330.29101@chino.kir.corp.google.com>
Date:	Thu, 26 May 2011 13:22:26 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Michael Rubin <mrubin@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] trace: Set oom_score_adj to maximum for ring buffer
 allocating process

On Thu, 26 May 2011, Steven Rostedt wrote:

> Hmm, have you tried this in practice? Yes we may kill the "echo" command
> but it doesn't stop the ring buffer from being allocated, and thus
> killing the echo command may not be enough, and those critical processes
> that you are trying to protect will be killed next.
> 
> Perhaps we should change the allocation of the ring buffer or detect OOM
> triggering. Maybe make all the allocations ATOMIC, thus it will be
> either available or not, and fail instead of trying to swap out other
> memory for the allocation.
> 

My impression of this was that it was attempting to avoid killing a 
different process by means of the oom killer rather than avoiding swap.  I 
don't think there's anything wrong with using GFP_KERNEL, but I'd suggest 
also using __GFP_NORETRY so the allocation calls into direct reclaim but 
will avoid oom killing anything and simply failing instead.
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