netdev - Re: [PATCH 1/2] socket: increase default maximum listen queue length

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Message-Id: <20110330.225254.104054904.davem@davemloft.net>
Date:	Wed, 30 Mar 2011 22:52:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	hagen@...u.net
Cc:	netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH 1/2] socket: increase default maximum listen queue
 length

From: Hagen Paul Pfeifer <hagen@...u.net>
Date: Fri, 25 Mar 2011 19:31:38 +0100

> sysctl_max_syn_backlog on the other hand provides similar functionality:
> provides a system wide upper limit of request sockets per listen socket.
> But sysctl_max_syn_backlog provides a more accurate value by considerate
> the actual memory situation of the system. 256 by default, 128 for
> systems with low memory and up to 1024 for larger systems.

sysctl_max_syn_backlog is not "256 by default", the calculation is:

	cnt = tcp_hashinfo.ehash_mask + 1;
 ...
	sysctl_max_syn_backlog = max(128, cnt / 256);

And I think we should leave the SOMAXCONN define alone (it's a
historic relic for userspace, and any sane server passes something
like ~0 into listen()).

And calculate the somaxconn sysctl at run time using a similar
formula to that used by sysctl_max_syn_backlog.
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