From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nivedita Singhvi Subject: Re: bad TSO performance in 2.6.9-rc2-BK Date: Wed, 22 Sep 2004 13:56:17 -0700 Sender: netdev-bounce@oss.sgi.com Message-ID: <4151E6F1.7000405@us.ibm.com> References: <20040920063012.GL2825@krispykreme> <20040920203021.GD4242@wotan.suse.de> <20040921155835.18aee381.davem@davemloft.net> <20040922140000.GD27432@wotan.suse.de> <20040922111209.7887df53.davem@davemloft.net> <20040922195515.GA2619@wotan.suse.de> <4151DB6C.8050906@us.ibm.com> <20040922133011.5885640b.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: ak@suse.de, anton@samba.org, netdev@oss.sgi.com Return-path: To: "David S. Miller" In-Reply-To: <20040922133011.5885640b.davem@davemloft.net> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org David S. Miller wrote: > The former rarely goes faster with TSO enabled simply > because there is sufficient cpu and bus bandwidth to > keep the card full. At about 700MHz (ok, old, I know) or thereabouts, it usually took > 1 CPU to drive a gigabit card, iirc, about 1.5 CPUs or so. > Whereas with something like SpecWEB the extra cpu and > bus cycles are needed by other resources of the benchmark > and thus performance goes up. Yep.. > I have no idea why people think TSO will make some single > stream TCP test go faster, it doesn't buy you more bytes > on the wire :-) True, if the card was already doing line speed, no, as you say, it won't help making the stack go faster :). If not, though, the gain in doing only one pass down the stack, one route look up, etc in place of multiple handoffs should help, correct? thanks, Nivedita