From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761351AbZDQPMS (ORCPT ); Fri, 17 Apr 2009 11:12:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758541AbZDQPMD (ORCPT ); Fri, 17 Apr 2009 11:12:03 -0400 Received: from smtp.ultrahosting.com ([74.213.174.254]:41682 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760475AbZDQPMB (ORCPT ); Fri, 17 Apr 2009 11:12:01 -0400 Date: Fri, 17 Apr 2009 11:04:41 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Peter Zijlstra cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: Scheduler regression: Too frequent timer interrupts(?) In-Reply-To: <1239979901.23397.4638.camel@laptop> Message-ID: References: <1239951613.23397.4107.camel@laptop> <1239977776.23397.4590.camel@laptop> <1239979901.23397.4638.camel@laptop> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 17 Apr 2009, Peter Zijlstra wrote: > And a random 1us cutoff, is well, random. Its got to be somewhere. > If you want to reduce interrupts, that's fine, but not counting an > interrupt because its below the magic 1us marker sounds a bit, well, > magic -- might work for you, might not for me on another machine, might > even be compiler dependent. The point is to reduce the interrupts of user space application. Hardware interrupts etc are something else. Maybe I should not use the term interrupt. Cpu unavailability? Cache pollution? > So 5 <1us interruption are not at all accounted, whereas a single 1>us > interruption is. I'd rather get rid of those 5 than try and shave a bit > of the one, if you get what I mean. Ok. We can set the threshold lower and see how that goes. > Furthermore, yes the scheduler is one of those jiffy tick users, but > there are more. We can do ntp/gtod things in there, there is process > accounting, there is some RCU machinery, timers etc.. Again things were fine before the scheduler changed. Could we defer interrupts if a single process is running on a cpu and there is no other process on the runqueue and no other use of the timer interrupt?