From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754631Ab0EQIwq (ORCPT ); Mon, 17 May 2010 04:52:46 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:46002 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754357Ab0EQIwo convert rfc822-to-8bit (ORCPT ); Mon, 17 May 2010 04:52:44 -0400 Subject: Re: commit e9e9250b: sync wakeup bustage when waker is an RT task From: Peter Zijlstra To: Mike Galbraith Cc: Ingo Molnar , LKML , Thomas Gleixner In-Reply-To: <1274086140.5605.3719.camel@twins> References: <1273924628.10630.24.camel@marge.simson.net> <1273925052.1674.138.camel@laptop> <1273943222.8752.7.camel@marge.simson.net> <1273994510.7873.10.camel@marge.simson.net> <1274071120.15000.10.camel@marge.simson.net> <1274086140.5605.3719.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 17 May 2010 10:52:25 +0200 Message-ID: <1274086345.5605.3727.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-05-17 at 10:49 +0200, Peter Zijlstra wrote: > On Mon, 2010-05-17 at 06:38 +0200, Mike Galbraith wrote: > > What would be the harm/consequence of restoring RT tasks to rq->load so > > the wake_affine()::sync logic just worked as before without hackery? > > Well, you'd have to constantly adjust the task weight of RT tasks to > reflect their actual consumption. Not really feasible. > > So the proportional stuff works like: > > slice_i = w_i / (\Sum_j w_j) * dt > > Giving a RT task a sensible weight we'd have to reverse that: > > w_i = slice_i/dt * (\Sum_j w_j) Another point to note is that this requires we track per-RT-task usage averages, whereas the cpu_power approach simply lumps everything !fair (one of the things still on the TODO list is account for IRQ overhead) into a single large bucket and doesn't care.