From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [RFC] [PATCH] Don't run __qdisc_run() on a stopped TX queue Date: Wed, 29 Jul 2009 12:47:34 +0000 Message-ID: <20090729124734.GD5490@ff.dom.local> References: <20090728024813.GA23992@gondor.apana.org.au> <20090727.212107.161491585.davem@davemloft.net> <20090728071247.GA25611@gondor.apana.org.au> <20090728.125919.146001472.davem@davemloft.net> <20090729004428.GA765@gondor.apana.org.au> <20090729110436.GA5490@ff.dom.local> <20090729111134.GA6478@gondor.apana.org.au> <20090729112614.GB5490@ff.dom.local> <20090729123041.GA7440@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , krkumar2@in.ibm.com, netdev@vger.kernel.org To: Herbert Xu Return-path: Received: from mail-fx0-f218.google.com ([209.85.220.218]:46992 "EHLO mail-fx0-f218.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751152AbZG2Mrl (ORCPT ); Wed, 29 Jul 2009 08:47:41 -0400 Received: by fxm18 with SMTP id 18so363706fxm.37 for ; Wed, 29 Jul 2009 05:47:41 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20090729123041.GA7440@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jul 29, 2009 at 08:30:41PM +0800, Herbert Xu wrote: > On Wed, Jul 29, 2009 at 11:26:14AM +0000, Jarek Poplawski wrote: > > > > If you mean the tx lock there should be no "real" contention: only > > one waiter max. qdisc lock's contention might be higher, but it's > > use (during contention) better: enqueue + dequeue together instead > > of doing it separately. > > Hmm, you will have contention if they're both transmitting a > single flow which must always go into a single physical queue. > > So you'll have two CPUs doing the work of a single CPU, with one > of them always spinning on the TX lock. Hmm.. I'd call it a little waiting, but OK let's call it contention;-) When tx is faster than queue operations there could be no contention at all. I'm not saying I must be right: IMHO it's only worth trying. Cheers, Jarek P.