From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] Bound TSO defer time (resend) Date: Mon, 16 Oct 2006 20:20:35 -0700 Message-ID: <20061016202035.6d55b96e@localhost.localdomain> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org Return-path: Received: from smtp.osdl.org ([65.172.181.4]:64913 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1422750AbWJQDU6 (ORCPT ); Mon, 16 Oct 2006 23:20:58 -0400 To: John Heffner In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, 16 Oct 2006 20:53:20 -0400 (EDT) John Heffner wrote: > The original message didn't show up on the list. I'm assuming it's > because the filters didn't like the attached postscript. I posted PDFs of > the figures on the web: > > http://www.psc.edu/~jheffner/tmp/a.pdf > http://www.psc.edu/~jheffner/tmp/b.pdf > http://www.psc.edu/~jheffner/tmp/c.pdf > > -John > > > ---------- Forwarded message ---------- > Date: Mon, 16 Oct 2006 15:55:53 -0400 (EDT) > From: John Heffner > To: David Miller > Cc: netdev > Subject: [PATCH] Bound TSO defer time > > This patch limits the amount of time you will defer sending a TSO segment > to less than two clock ticks, or the time between two acks, whichever is > longer. > > On slow links, deferring causes significant bursts. See attached plots, > which show RTT through a 1 Mbps link with a 100 ms RTT and ~100 ms queue > for (a) non-TSO, (b) currnet TSO, and (c) patched TSO. This burstiness > causes significant jitter, tends to overflow queues early (bad for short > queues), and makes delay-based congestion control more difficult. > > Deferring by a couple clock ticks I believe will have a relatively small > impact on performance. > > > Signed-off-by: John Heffner Okay, but doing any timing on clock ticks makes the behavior dependent on the value of HZ which doesn't seem desirable. Should this be based on RTT or a real-time values?