From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: tcp bw in 2.6 Date: Tue, 2 Oct 2007 10:10:55 -0700 Message-ID: <20071002101055.219753cd@freepuppy.rosehill> References: <20071002005917.GB5480@bitmover.com> <20071002150935.GC17418@bitmover.com> <20071002154137.GD17418@bitmover.com> <20071002162534.GG17418@bitmover.com> <20071002094726.154fc619@freepuppy.rosehill> <20071002164952.GI17418@bitmover.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Larry McVoy , Herbert Xu , torvalds@linux-foundation.org, davem@davemloft.net, wscott@bitmover.com, netdev@vger.kernel.org To: lm@bitmover.com (Larry McVoy) Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:37113 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753017AbXJBRMQ (ORCPT ); Tue, 2 Oct 2007 13:12:16 -0400 In-Reply-To: <20071002164952.GI17418@bitmover.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 2 Oct 2007 09:49:52 -0700 lm@bitmover.com (Larry McVoy) wrote: > On Tue, Oct 02, 2007 at 09:47:26AM -0700, Stephen Hemminger wrote: > > On Tue, 2 Oct 2007 09:25:34 -0700 > > lm@bitmover.com (Larry McVoy) wrote: > > > > > > If the server side is the source of the data, i.e, it's transfer is a > > > > write loop, then I get the bad behaviour. > > > > ... > > > > So is this a bug or intentional? > > > > > > For whatever it is worth, I believed that we used to get better performance > > > from the same hardware. My guess is that it changed somewhere between > > > 2.6.15-1-k7 and 2.6.18-5-k7. > > > > For the period from 2.6.15 to 2.6.18, the kernel by default enabled TCP > > Appropriate Byte Counting. This caused bad performance on applications that > > did small writes. > > It's doing 1MB writes. > > Is there a sockopt to turn that off? Or /proc or something? sysctl -w net.ipv4.tcp_abc=0 -- Stephen Hemminger