From: Jesse Barnes <jbarnes@sgi.com>
To: Nick Piggin <piggin@cyberone.com.au>
Subject: Re: [PATCH] Remove OOM killer from try_to_free_pages / all_unreclaimable braindamage
Date: Fri, 5 Nov 2004 17:36:24 -0800
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Cc: Andrea Arcangeli <andrea@novell.com>,
       Marcelo Tosatti <marcelo.tosatti@cyclades.com>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org
References: <20041105200118.GA20321@logos.cnet> <20041106012018.GT8229@dualathlon.random> <418C2861.6030501@cyberone.com.au>
In-Reply-To: <418C2861.6030501@cyberone.com.au>
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On Friday, November 05, 2004 5:26 pm, Nick Piggin wrote:
> >If you move it in kswapd there's no way to prevent oom-killing from a
> >syscall allocation (I guess even right now it would go wrong in this
> >sense, but at least right now it's more fixable). I want to move the oom
> >kill outside the alloc_page paths. The oom killing is all about the page
> >faults not having a fail path, and in turn the oom killing should be
> >moved in the page fault code, not in the allocator. Everything else
> >should keep returning -ENOMEM to the caller.
>
> Probably a good idea. OTOH, some kernel allocations might really
> need to be performed and have no failure path. For example __GFP_REPEAT.

Ah, I see what you're saying, yes, that makes even more sense :)

> I think maybe __GFP_REPEAT allocations at least should be able to
> cause an OOM. Not sure though.
>
> >So to me moving the oom killer into kswapd looks a regression.
>
> Also, I think it would do the wrong thing on NUMA machines because
> that has a per-node kswapd.

Yep, Andrea's explaination is clear, I just had to read it a few times.  
Anyway, the fixes I posted are still necessary I think.

Thanks,
Jesse
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