From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neal Cardwell Subject: Re: limited network bandwidth with 3.2.x kernels Date: Thu, 16 Feb 2012 12:22:29 -0500 Message-ID: References: <1329399616.9395.9.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> <1329400265.3048.178.camel@deadeye> <1329404975.10004.3.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> <20120216.120149.437368615973561397.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: eric.dumazet@gmail.com, bhutchings@solarflare.com, netdev@vger.kernel.org, alekcejk@googlemail.com To: David Miller Return-path: Received: from mail-qw0-f46.google.com ([209.85.216.46]:51832 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753837Ab2BPRWa (ORCPT ); Thu, 16 Feb 2012 12:22:30 -0500 Received: by qadc10 with SMTP id c10so4642146qad.19 for ; Thu, 16 Feb 2012 09:22:29 -0800 (PST) In-Reply-To: <20120216.120149.437368615973561397.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: Our team has also run into issues with GRO/LRO "stretch ACKs", and their negative impact on TCP performance. We have a patch that we've been working with that deals with the sender-side issues. It turns out that neither the ABC nor non-ABC byte counting quite fixes the stretch ACKs issues. On the receiver side, the approach of changing tcp_grow_window() and __tcp_grow_window() to adjust things in terms of actual packet size rather than a fixed 2*MSS sounds great to me as well. In terms of the original 3.1 vs 3.2 issue report that started this thread, I didn't see any evidence of LRO or GRO causing stretch ACKs. (Alexey, would you be able to confim by running "ethtool -k eth0" on both kernels?) So it seems that probably the original issue is unrelated to stretch ACKs? neal