Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761628AbXHWMN5 (ORCPT ); Thu, 23 Aug 2007 08:13:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758250AbXHWMNt (ORCPT ); Thu, 23 Aug 2007 08:13:49 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:42603 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757727AbXHWMNs (ORCPT ); Thu, 23 Aug 2007 08:13:48 -0400 Date: Thu, 23 Aug 2007 14:13:41 +0200 From: Ingo Molnar To: "Siddha, Suresh B" Cc: nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [patch] sched: fix broken smt/mc optimizations with CFS Message-ID: <20070823121341.GA5775@elte.hu> References: <20070816010150.GG10033@linux-os.sc.intel.com> <20070823115416.GA31027@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070823115416.GA31027@elte.hu> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2354 Lines: 65 * Ingo Molnar wrote: > [...] So how about the patch below instead? the right patch attached. --------------------------------> Subject: sched: fix broken SMT/MC optimizations From: "Siddha, Suresh B" On a four package system with HT - HT load balancing optimizations were broken. For example, if two tasks end up running on two logical threads of one of the packages, scheduler is not able to pull one of the tasks to a completely idle package. In this scenario, for nice-0 tasks, imbalance calculated by scheduler will be 512 and find_busiest_queue() will return 0 (as each cpu's load is 1024 > imbalance and has only one task running). Similarly MC scheduler optimizations also get fixed with this patch. [ mingo@elte.hu: restored fair balancing by increasing the fuzz and adding it back to the power decision, without the /2 factor. ] Signed-off-by: Suresh Siddha Signed-off-by: Ingo Molnar --- include/linux/sched.h | 2 +- kernel/sched.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) Index: linux/include/linux/sched.h =================================================================== --- linux.orig/include/linux/sched.h +++ linux/include/linux/sched.h @@ -681,7 +681,7 @@ enum cpu_idle_type { #define SCHED_LOAD_SHIFT 10 #define SCHED_LOAD_SCALE (1L << SCHED_LOAD_SHIFT) -#define SCHED_LOAD_SCALE_FUZZ (SCHED_LOAD_SCALE >> 1) +#define SCHED_LOAD_SCALE_FUZZ SCHED_LOAD_SCALE #ifdef CONFIG_SMP #define SD_LOAD_BALANCE 1 /* Do load balancing on this domain. */ Index: linux/kernel/sched.c =================================================================== --- linux.orig/kernel/sched.c +++ linux/kernel/sched.c @@ -2517,7 +2517,7 @@ group_next: * a think about bumping its value to force at least one task to be * moved */ - if (*imbalance + SCHED_LOAD_SCALE_FUZZ < busiest_load_per_task/2) { + if (*imbalance + SCHED_LOAD_SCALE_FUZZ < busiest_load_per_task) { unsigned long tmp, pwr_now, pwr_move; unsigned int imbn; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/