Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424487AbWKKCFa (ORCPT ); Fri, 10 Nov 2006 21:05:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1424494AbWKKCFa (ORCPT ); Fri, 10 Nov 2006 21:05:30 -0500 Received: from mga03.intel.com ([143.182.124.21]:4152 "EHLO mga03.intel.com") by vger.kernel.org with ESMTP id S1424487AbWKKCF3 (ORCPT ); Fri, 10 Nov 2006 21:05:29 -0500 X-ExtLoop1: 1 X-IronPort-AV: i="4.09,412,1157353200"; d="scan'208"; a="144497088:sNHT17508288" From: "Chen, Kenneth W" To: "'Christoph Lameter'" , "Ingo Molnar" Cc: "Siddha, Suresh B" , , , , Subject: RE: + sched-use-tasklet-to-call-balancing.patch added to -mm tree Date: Fri, 10 Nov 2006 18:05:28 -0800 Message-ID: <000701c70535$dc0d8e70$ff0da8c0@amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 Thread-Index: AccFLPPyDLav2pLzR4aRqnlmB1vH+AACCuyg X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1385 Lines: 26 Christoph Lameter wrote on Friday, November 10, 2006 5:01 PM > On Fri, 10 Nov 2006, Ingo Molnar wrote: > > > ok, that's what i suspected - what made the difference wasnt the fact > > that it was moved out of irqs-off section, but that it was running > > globally, instead of in parallel on every cpu. I have no conceptual > > problem with single-threading the more invasive load-balancing bits. > > (since it has to touch every runqueue anyway there's probably little > > parallelism possible) But it's a scary change nevertheless, it > > materially affects every SMP system's balancing characteristics. > > We saw multiple issues. The first we saw was interrupt holdoff related > since IPIs took a long time to complete. The other was that multiple > load balance actions in multiple CPUs seem to serialize on the locks > trying each to move tasks off the same busy processor. So both better be > addressed. So designate only one CPU within a domain to do load balance between groups for that specific sched domain should in theory fix the 2nd problem you identified. Did you get a chance to look at the patch Suresh posted? - 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/