From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [ofa-general] Re: [PATCH 2/3][NET_BATCH] net core use batching Date: Wed, 10 Oct 2007 03:44:46 -0700 (PDT) Message-ID: <20071010.034446.85819294.davem@davemloft.net> References: <20071010091644.GA9807@one.firstfloor.org> <20071010.022550.21928751.davem@davemloft.net> <20071010102331.GA10496@one.firstfloor.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: hadi@cyberus.ca, shemminger@linux-foundation.org, jeff@garzik.org, johnpol@2ka.mipt.ru, herbert@gondor.apana.org.au, gaagaan@gmail.com, Robert.Olsson@data.slu.se, netdev@vger.kernel.org, rdreier@cisco.com, peter.p.waskiewicz.jr@intel.com, mcarlson@broadcom.com, jagana@us.ibm.com, general@lists.openfabrics.org, mchan@broadcom.com, tgraf@suug.ch, randy.dunlap@oracle.com, sri@us.ibm.com, kaber@trash.net To: andi@firstfloor.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:35773 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752479AbXJJKoo (ORCPT ); Wed, 10 Oct 2007 06:44:44 -0400 In-Reply-To: <20071010102331.GA10496@one.firstfloor.org> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Andi Kleen Date: Wed, 10 Oct 2007 12:23:31 +0200 > On Wed, Oct 10, 2007 at 02:25:50AM -0700, David Miller wrote: > > The chip I was working with at the time (UltraSPARC-IIi) compressed > > all the linear stores into 64-byte full cacheline transactions via > > the store buffer. > > That's a pretty old CPU. Conclusions on more modern ones might be different. Cache matters, just scale the numbers. > I suppose it would be an interesting experiment at least. Absolutely. I've always gotten very poor results when increasing the TX queue a lot, for example with NIU the point of diminishing returns seems to be in the range of 256-512 TX descriptor entries and this was with 1.6Ghz cpus.