From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: TCPBacklogDrops during aggressive bursts of traffic Date: Fri, 18 May 2012 17:49:36 +0200 Message-ID: <1337356176.7029.47.camel@edumazet-glaptop> References: <1337092718.1689.45.camel@kjm-desktop.uk.level5networks.com> <1337093776.8512.1089.camel@edumazet-glaptop> <1337099368.1689.47.camel@kjm-desktop.uk.level5networks.com> <1337099641.8512.1102.camel@edumazet-glaptop> <1337100454.2544.25.camel@bwh-desktop.uk.solarflarecom.com> <1337101280.8512.1108.camel@edumazet-glaptop> <1337272292.1681.16.camel@kjm-desktop.uk.level5networks.com> <1337272654.3403.20.camel@edumazet-glaptop> <1337355955.15044.24.camel@kjm-desktop.uk.level5networks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Ben Hutchings , netdev@vger.kernel.org To: Kieran Mansley Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:51366 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757200Ab2ERPtp (ORCPT ); Fri, 18 May 2012 11:49:45 -0400 Received: by bkcji2 with SMTP id ji2so2468347bkc.19 for ; Fri, 18 May 2012 08:49:44 -0700 (PDT) In-Reply-To: <1337355955.15044.24.camel@kjm-desktop.uk.level5networks.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2012-05-18 at 16:45 +0100, Kieran Mansley wrote: > On Thu, 2012-05-17 at 18:37 +0200, Eric Dumazet wrote: > > > > Hmm, I was not suggesting running production servers with this > > setting, only do an experiment. > > OK. I've found a more reliable way to reproduce it (use MSG_WAITALL to > make the recv call wait till the socket buffer will be more full) and > tried with the tcp_adv_win_scale to -2. It's hard to make any confident > assertions about the impact of it, but if it does change the behaviour > it is a small change. There are certainly still plenty of drops with > that setting. Are you playing with SO_RCVBUF, or let the stack autotune it ?