From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753927Ab2GZWBY (ORCPT ); Thu, 26 Jul 2012 18:01:24 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35909 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753802Ab2GZWBU (ORCPT ); Thu, 26 Jul 2012 18:01:20 -0400 Date: Thu, 26 Jul 2012 23:01:07 +0100 From: Ben Hutchings To: Peter Zijlstra Cc: stable@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Ingo Molnar , LKML Message-ID: <20120726220107.GG1894@decadent.org.uk> References: <20120723010655.768372060@decadent.org.uk> <1343138818.5132.98.camel@deadeye.wl.decadent.org.uk> <1343337937.32120.20.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1343337937.32120.20.camel@twins> User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: ben@decadent.org.uk Subject: Re: [ 028/108] sched/nohz: Rewrite and fix load-avg computation -- again X-SA-Exim-Version: 4.2.1 (built Mon, 22 Mar 2010 06:51:10 +0000) X-SA-Exim-Scanned: Yes (on shadbolt.decadent.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 26, 2012 at 11:25:37PM +0200, Peter Zijlstra wrote: > On Tue, 2012-07-24 at 15:06 +0100, Ben Hutchings wrote: > > On Mon, 2012-07-23 at 02:07 +0100, Ben Hutchings wrote: > > > 3.2-stable review patch. If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Peter Zijlstra > > > > > > commit 5167e8d5417bf5c322a703d2927daec727ea40dd upstream. > > > > > > Thanks to Charles Wang for spotting the defects in the current code: > > > > > > - If we go idle during the sample window -- after sampling, we get a > > > negative bias because we can negate our own sample. > > > > > > - If we wake up during the sample window we get a positive bias > > > because we push the sample to a known active period. > > > > > > So rewrite the entire nohz load-avg muck once again, now adding > > > copious documentation to the code. > > [...] > > > > Based on , I think we also need: > > > > 556061b sched/nohz: Fix rq->cpu_load[] calculations > > 5aaa0b7 sched/nohz: Fix rq->cpu_load calculations some more > > > > Does this ('sched/nohz: Rewrite and fix load-avg computation -- again') > > depend in any way on those, or are they separate fixes? > > they might touch on a few entry points but the logic is separate. > > ->cpu_load[] is per-cpu weight tracking for the load-balancer. That's what I thought, so I went ahead with just the one. Should I queue up the other two for a future 3.2.y update? Ben. -- Ben Hutchings We get into the habit of living before acquiring the habit of thinking. - Albert Camus