Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757142AbXH1W13 (ORCPT ); Tue, 28 Aug 2007 18:27:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751617AbXH1W1W (ORCPT ); Tue, 28 Aug 2007 18:27:22 -0400 Received: from mga02.intel.com ([134.134.136.20]:59859 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751409AbXH1W1U (ORCPT ); Tue, 28 Aug 2007 18:27:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.19,318,1183359600"; d="scan'208";a="284996613" Date: Tue, 28 Aug 2007 15:27:19 -0700 From: "Siddha, Suresh B" To: mingo@elte.hu Cc: Ingo Molnar , 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: <20070828222718.GI1894@linux-os.sc.intel.com> References: <20070816010150.GG10033@linux-os.sc.intel.com> <20070823115416.GA31027@elte.hu> <20070823121341.GA5775@elte.hu> <20070827191905.GE1894@linux-os.sc.intel.com> <20070827192324.GA29441@elte.hu> <20070827193103.GF1894@linux-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070827193103.GF1894@linux-os.sc.intel.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2206 Lines: 67 On Mon, Aug 27, 2007 at 12:31:03PM -0700, Siddha, Suresh B wrote: > Essentially I observed that nice 0 tasks still endup on two cores of same > package, with out getting spread out to two different packages. This behavior > is same with out this fix and this fix doesn't help in any way. Ingo, Appended patch seems to fix the issue and as far as I can test, seems ok to me. This is a quick fix for .23. Peter Williams and myself plan to look at code cleanups in this area (HT/MC optimizations) post .23 BTW, with this fix, do you want to retain the current FUZZ value? thanks, suresh -- Try to fix MC/HT scheduler optimization breakage again, with out breaking the FUZZ logic. First fix the check if (*imbalance + SCHED_LOAD_SCALE_FUZZ < busiest_load_per_task) with this if (*imbalance < busiest_load_per_task) As the current check is always false for nice 0 tasks (as SCHED_LOAD_SCALE_FUZZ is same as busiest_load_per_task for nice 0 tasks). With the above change, imbalance was getting reset to 0 in the corner case condition, making the FUZZ logic fail. Fix it by not corrupting the imbalance and change the imbalance, only when it finds that the HT/MC optimization is needed. Signed-off-by: Suresh Siddha --- diff --git a/kernel/sched.c b/kernel/sched.c index 9fe473a..03e5e8d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2511,7 +2511,7 @@ 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) { + if (*imbalance < busiest_load_per_task) { unsigned long tmp, pwr_now, pwr_move; unsigned int imbn; @@ -2563,10 +2563,8 @@ small_imbalance: pwr_move /= SCHED_LOAD_SCALE; /* Move if we gain throughput */ - if (pwr_move <= pwr_now) - goto out_balanced; - - *imbalance = busiest_load_per_task; + if (pwr_move > pwr_now) + *imbalance = busiest_load_per_task; } return busiest; - 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/