Message-ID: <44DDE857.3080703@redhat.com>
Date: Sat, 12 Aug 2006 10:40:23 -0400
From: Rik van Riel <riel@redhat.com>
Organization: Red Hat, Inc
User-Agent: Thunderbird 1.5.0.4 (X11/20060614)
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To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
       Daniel Phillips <phillips@google.com>
Subject: Re: [RFC][PATCH 0/9] Network receive deadlock prevention for NBD
References: <20060808193325.1396.58813.sendpatchset@lappy> <20060809054648.GD17446@2ka.mipt.ru> <1155127040.12225.25.camel@twins> <20060809130752.GA17953@2ka.mipt.ru> <1155130353.12225.53.camel@twins> <44DD4E3A.4040000@redhat.com> <20060812084713.GA29523@2ka.mipt.ru> <1155374390.13508.15.camel@lappy> <20060812093706.GA13554@2ka.mipt.ru>
In-Reply-To: <20060812093706.GA13554@2ka.mipt.ru>
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Evgeniy Polyakov wrote:
> On Sat, Aug 12, 2006 at 11:19:49AM +0200, Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:
>>> As you described above, memory for each packet must be allocated (either
>>> from SLAB or from reserve), so network needs special allocator in OOM
>>> condition, and that allocator should be separated from SLAB's one which 
>>> got OOM, so my purpose is just to use that different allocator (with
>>> additional features) for netroking always.
> 
> No it is not. There are socket queues and they are limited. Things like
> TCP behave even better.

Ahhh, but there are two allocators in play here.

The first one allocates the memory for receiving packets.
This can be one pool, as long as it is isolated from
other things in the system it is fine.

The second allocator allocates more memory for socket
buffers.  The memory critical sockets should get their
memory from a mempool, once normal socket memory
allocations start failing.

This means our allocation differentiation only needs
to happen at the socket stage.

Or am I overlooking something?

-- 
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan
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