netdev - Re: [PATCH] tcp: Fix slowness in read /proc/net/tcp

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Date:	Mon, 07 Jun 2010 00:55:56 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	therbert@...gle.com, netdev@...r.kernel.org, iler.ml@...il.com
Subject: Re: [PATCH] tcp: Fix slowness in read /proc/net/tcp

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 07 Jun 2010 09:19:27 +0200

> Le dimanche 06 juin 2010 à 20:27 -0700, Tom Herbert a écrit :
>> Signed-off-by: Tom Herbert <therbert@...gle.com>
>> ---
> 
> This problem raises every year,  (last attempt from Yakov Lerner :
> http://kerneltrap.org/mailarchive/linux-netdev/2009/9/26/6256119 )
> 
> And finally, someone motivated enough to use /proc/net/tcp found the
> right answer ;)
> 
> Most netdev people tend to push inet_diag (netlink) interface instead of
> old /proc/net/tcp, but it seems old interface will still be used in
> 2030, so :
> 
> Acked-by: Eric Dumazet <eric.dumazet@...il.com>

Indeed this is the best attempt of this I've seen so far,
applied to net-next-2.6, thanks Tom.

> BTW, another problem of /proc/net/tcp is the buffer size used by netstat
> utility : 1024 bytes instead of PAGE_SIZE, making O(N^2) behavior even
> more palpable.

Probably cap it at 8K like we do for netlink atomic reads, because
there are all sorts of crazy PAGE_SIZE configurations possible out
there, even as high as 512K.
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