From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263265AbTEIQmU (ORCPT ); Fri, 9 May 2003 12:42:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263311AbTEIQmU (ORCPT ); Fri, 9 May 2003 12:42:20 -0400 Received: from holomorphy.com ([66.224.33.161]:2209 "EHLO holomorphy") by vger.kernel.org with ESMTP id S263265AbTEIQmT (ORCPT ); Fri, 9 May 2003 12:42:19 -0400 Date: Fri, 9 May 2003 09:53:59 -0700 From: William Lee Irwin III To: Robert Love Cc: Chris Friesen , Linux Kernel Mailing List Subject: Re: how to measure scheduler latency on powerpc? realfeel doesn't work due to /dev/rtc issues Message-ID: <20030509165359.GX8978@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Robert Love , Chris Friesen , Linux Kernel Mailing List References: <20030509003825.GR8978@holomorphy.com> <3EBB25FD.7060809@nortelnetworks.com> <20030509042659.GS8978@holomorphy.com> <3EBB4735.30701@nortelnetworks.com> <20030509062008.GT8978@holomorphy.com> <3EBB504C.1030001@nortelnetworks.com> <20030509070142.GU8978@holomorphy.com> <1052498824.867.8.camel@icbm> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1052498824.867.8.camel@icbm> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2003-05-09 at 03:01, William Lee Irwin III wrote: >> Why not just keep track of it in the scheduler? The statistic is well- >> defined in terms of things measurable at context switch and wakeup. On Fri, May 09, 2003 at 12:47:05PM -0400, Robert Love wrote: > This would measure context switch latency. Or something. > By definition, scheduling latency is the time from an interrupt which > wakes the task up until the task is actually running. > Historically, it has been measured by things like realfeel or amlat or > whatever which generate interrupts and wake a waiting task up. You then > measure the latency between the interrupt and when the task actually > runs in user-space. > So Chris can then go run this test under varying loads and see how bad > the latency gets. I understand his question, but (sorry Chris) I have > no idea of the solution on PPC. Not at all. Just stamp at wakeup and difference when it runs. -- wli