From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 19 Sep 2001 22:56:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 19 Sep 2001 22:56:10 -0400 Received: from blount.mail.mindspring.net ([207.69.200.226]:35845 "EHLO blount.mail.mindspring.net") by vger.kernel.org with ESMTP id ; Wed, 19 Sep 2001 22:56:03 -0400 Subject: Re: [PATCH] Preemption Latency Measurement Tool From: Robert Love To: David Lang Cc: safemode , linux-kernel@vger.kernel.org In-Reply-To: In-Reply-To: Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Evolution-Format: text/plain X-Mailer: Evolution/0.13.99+cvs.2001.09.19.07.08 (Preview Release) Date: 19 Sep 2001 22:57:27 -0400 Message-Id: <1000954648.4340.91.camel@phantasy> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2001-09-19 at 21:13, David Lang wrote: > also how useful is the latency info once swapping starts? if you have > something that gets swapped out it will have horrible latency and skew the > results (or at the very least you won't know if the problem is disk IO or > fixable problems) Its not that bad because the patch measures latency across points where preemption was enabled and disabled -- the various kernel locking mechanisms. Thus either page fault holds a lock and it is a legimate latency recorded over that specific lock, or it doesn't in which case its not an issue. -- Robert M. Love rml at ufl.edu rml at tech9.net