From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: [PATCH 2/2] socket: add minimum listen queue length sysctl Date: Fri, 25 Mar 2011 13:24:37 -0700 Message-ID: <1301084677.13505.26.camel@tardy> References: <1301077899-16482-1-git-send-email-hagen@jauu.net> <1301077899-16482-2-git-send-email-hagen@jauu.net> Reply-To: rick.jones2@hp.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Eric Dumazet To: Hagen Paul Pfeifer Return-path: Received: from g4t0017.houston.hp.com ([15.201.24.20]:35441 "EHLO g4t0017.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682Ab1CYUYm (ORCPT ); Fri, 25 Mar 2011 16:24:42 -0400 In-Reply-To: <1301077899-16482-2-git-send-email-hagen@jauu.net> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2011-03-25 at 19:31 +0100, Hagen Paul Pfeifer wrote: > In the case that a server programmer misjudge network characteristic the > backlog parameter for listen(2) may not adequate to utilize hosts > capabilities and lead to unrequired SYN retransmission - thus a > underestimated backlog value can form an artificial limitation. > > A listen queue length of 8 is often a way to small, but several > server authors does not about know this limitation (from Erics server > setup): > > ss -a | head > State Recv-Q Send-Q Local Address:Port Peer > Address:Port > LISTEN 0 8 *:imaps *:* > LISTEN 0 8 *:pop3s *:* > LISTEN 0 50 *:mysql *:* > LISTEN 0 8 *:pop3 *:* > LISTEN 0 8 *:imap2 *:* > LISTEN 0 511 *:www *:* > > Until now it was not possible for the system (network) administrator to > increase this value. A bug report must be filled, the backlog increased, > a new version released or even worse: if using closed source software > you cannot make anything. Well, one could LD_PRELOAD something that intercepted listen() calls no? > sysctl_min_syn_backlog provides the ability to increase the minimum > queue length. Is there already a similar minimum the admin can configure when the applications makes "too small" an explicit setsockopt() call against SO_SNDBUF or SO_RCVBUF? rick jones