From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kieran Mansley Subject: Re: TCPBacklogDrops during aggressive bursts of traffic Date: Thu, 17 May 2012 17:31:29 +0100 Message-ID: <1337272292.1681.16.camel@kjm-desktop.uk.level5networks.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Ben Hutchings , To: Eric Dumazet Return-path: Received: from webmail.solarflare.com ([12.187.104.25]:29340 "EHLO ocex02.SolarFlarecom.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932172Ab2EQQbd (ORCPT ); Thu, 17 May 2012 12:31:33 -0400 In-Reply-To: <1337101280.8512.1108.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-05-15 at 19:01 +0200, Eric Dumazet wrote: > You could try setting tcp_adv_win_scale to -2 I've been unable to reproduce this at all this afternoon (not sure why) so haven't been able to try that suggestion yet. >>From looking in to what it does it sounds like it could well help, but only in the sense of tuning the system to make it harder to hit the race rather than fixing the race altogether. Similarly for fixing skb->truesize (we spotted this last week when we first hit the problem, and adjusting it didn't make much difference). I'll take another look tomorrow and see if I can work out what's changed to make the drops disappear. Kieran