linux-kernel - Re: [patch 5/5] oom: invoke OOM killer from pagefault handler

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Message-Id: <20061012150942.42e05898.akpm@osdl.org>
Date:	Thu, 12 Oct 2006 15:09:42 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Kirill Korotaev <dev@...ru>,
	Linux Memory Management <linux-mm@...ck.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch 5/5] oom: invoke OOM killer from pagefault handler

On Thu, 12 Oct 2006 17:19:07 +0200
Nick Piggin <npiggin@...e.de> wrote:

> On Thu, Oct 12, 2006 at 07:12:13PM +0400, Kirill Korotaev wrote:
> > Nick,
> > 
> > AFAICS, 1 page allocation which is done in page fault handler
> > can fail in the only case - OOM kills current, so if we failed
> > we should have TIF_MEMDIE and just kill current.
> > Selecting another process for killing if page fault fails means
> > taking another victim with the one being already killed.
> > 
> 
> Hi Kirill,
> 
> I don't quite understand you.

Kirill is claiming that the only occasion on which a pagefault handler would
get an oom is when it killed itself in the oom handler.

> If the page allocation fails in the
> fault handler, we don't want to kill current if it is marked as
> OOM_DISABLE or sysctl_panic_on_oom is set... imagine a critical
> service in a failover system.
> 
> It should be quite likely for another process to be kiled and
> provide enough memory to keep the system running. Presuming you
> have faith in the concept of the OOM killer ;)

I'm a bit wobbly about this one.  Some before-and-after testing results
would help things along..
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