From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932090AbWCOW1E (ORCPT ); Wed, 15 Mar 2006 17:27:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932079AbWCOW1E (ORCPT ); Wed, 15 Mar 2006 17:27:04 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:34188 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S932090AbWCOW1B (ORCPT ); Wed, 15 Mar 2006 17:27:01 -0500 Date: Wed, 15 Mar 2006 23:24:41 +0100 From: Ingo Molnar To: Jeff Garzik Cc: Lee Revell , "Bill Rugolsky Jr." , Andi Kleen , Jason Baron , linux-kernel@vger.kernel.org, john stultz Subject: Re: libata/sata_nv latency on NVIDIA CK804 [was Re: AMD64 X2 lost ticks on PM timer] Message-ID: <20060315222441.GA24074@elte.hu> References: <200602280022.40769.darkray@ic3man.com> <4408BEB5.7000407@garzik.org> <20060303234330.GA14401@ti64.telemetry-investments.com> <200603040107.27639.ak@suse.de> <20060315213638.GA17817@ti64.telemetry-investments.com> <1142459152.1671.64.camel@mindpipe> <20060315215848.GB18241@elte.hu> <441893AB.1070300@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <441893AB.1070300@garzik.org> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.5 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] 0.8 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Jeff Garzik wrote: > Ingo Molnar wrote: > >in this particular case there's only very simple (and non-IO) > >instructions in that codepath (no loops either), except for > >ata_bmdma_status() which does IO ops: so i agree with you that the most > >likely candidate for the delay is the readb() or the inb() in > >ata_bdma_status(). > > > >I'm wondering which one of the two. inb()s are known to be horrible on > >some systems - but i've never seen them take 16 milliseconds. If it's > >the inb(), then that could also involve SMM mode and IO > > > ata_bmdma_status() is just a single IO read, and even 1ms is highly > improbable. well, it's a PIO inb() op i think, and could thus in theory trigger SMM BIOS code. > I'd look elsewhere. There are a ton of udelay() calls in the legacy > PCI IDE BMDMA code paths (sata_nv uses these), so I'm not surprised > there is latency in general, in a libata+sata_nv configuration. [...] they would show up in the latency trace ... the latency trace is very clear, and in the previous mail i described the precise codepath where we observed the latency. Only that single PIO read is there AFAICS. Ingo