netdev - [RFC] socket sk_sndmsg

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Message-ID: <1323154416.2467.27.camel@edumazet-laptop>
Date:	Tue, 06 Dec 2011 07:53:36 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [RFC] socket sk_sndmsg_page waste

TCP can steer one page of memory per socket to cook outgoing frames.

This means a machine handling long living sockets can consume a lot of
ram.

1.000.000 tcp sockets : up to 4GB of allocated memory, if some writes
had been done on these sockets.

It would make sense to use a per thread page as a pool, instead of a per
socket pool, and remove sk_sndmsg_page/off fields.

Problem with this strategy is impact outside of net tree, and a cost at
thread creation/destruction.

[ But this could be used in fs/pipe.c or fs/splice.c code..., so that
small writes() dont allocate a full page but try to reuse the "per
task_struct" page ]

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