Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751272AbVJJVjg (ORCPT ); Mon, 10 Oct 2005 17:39:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751274AbVJJVjg (ORCPT ); Mon, 10 Oct 2005 17:39:36 -0400 Received: from gateway-1237.mvista.com ([12.44.186.158]:25332 "EHLO hermes.mvista.com") by vger.kernel.org with ESMTP id S1751272AbVJJVjg (ORCPT ); Mon, 10 Oct 2005 17:39:36 -0400 Subject: Re: Latency data - 2.6.14-rc3-rt13 From: Daniel Walker To: Mark Knecht Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Lee Revell In-Reply-To: <5bdc1c8b0510101412n714c4798v1482254f6f8e0386@mail.gmail.com> References: <5bdc1c8b0510101316k23ff64e2i231cdea7f11e8553@mail.gmail.com> <1128977359.18782.199.camel@c-67-188-6-232.hsd1.ca.comcast.net> <5bdc1c8b0510101412n714c4798v1482254f6f8e0386@mail.gmail.com> Content-Type: text/plain Date: Mon, 10 Oct 2005 14:39:32 -0700 Message-Id: <1128980373.18782.205.camel@c-67-188-6-232.hsd1.ca.comcast.net> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1602 Lines: 46 On Mon, 2005-10-10 at 14:12 -0700, Mark Knecht wrote: > On 10/10/05, Daniel Walker wrote: > > On Mon, 2005-10-10 at 13:16 -0700, Mark Knecht wrote: > > > Hi, > > > > > > > > How can I get data that would be more useful in terms of real debug? > > > > The IRQ off times look like the worst . If you do "make menuconfig" > > > > then goto Kernel Hacking and select > > "Interrupts-off critical section latency timing" > > Then select "Latency tracing" > > > > Then when you boot the system before run the following, > > > > "echo 0 > /proc/sys/kernel/preempt_max_latency" > > So this disables the tracing of preempt times but keeps IRQ times on? Cool. Yes, that what the compile options are doing. > > > > That will record a trace for every maximum latency observed for IRQ > > latency . You can view the trace with this command > > "cat /proc/latency_trace" , and you can attach the trace to an email to > > LKML so we can review it (compress it if it's big though) . > > > > Daniel > > Will do. Building now. I'll be back later. > > Is there anything specific I should look for in the traces myself? > Anyway to help narrow it down? You want the trace to represent the largest latency. For instance in the histogram it showed IRQ latency was ~3000us or greater, so you want the trace to show at least that size latency . Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/