From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932249AbZJLOVx (ORCPT ); Mon, 12 Oct 2009 10:21:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932222AbZJLOVw (ORCPT ); Mon, 12 Oct 2009 10:21:52 -0400 Received: from viefep12-int.chello.at ([62.179.121.32]:31005 "EHLO viefep12-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932212AbZJLOVw (ORCPT ); Mon, 12 Oct 2009 10:21:52 -0400 X-SourceIP: 213.93.53.227 Subject: Re: hackbench regression with kernel 2.6.32-rc1 From: Peter Zijlstra To: "Zhang, Yanmin" Cc: LKML , Ingo Molnar , Mike Galbraith In-Reply-To: <1255331120.3684.43.camel@ymzhang> References: <1255079943.25078.23.camel@ymzhang> <1255084986.8802.46.camel@laptop> <1255331120.3684.43.camel@ymzhang> Content-Type: text/plain Date: Mon, 12 Oct 2009 16:21:04 +0200 Message-Id: <1255357264.10420.15.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2009-10-12 at 15:05 +0800, Zhang, Yanmin wrote: > > So hackbench is a multi-cast, with one sender spraying multiple > > receivers, who in their turn don't spray back, right? > Right. volanoMark has about 9% regression on stoakley and 50% regression > on tigerton. If I revert the original patches, volanoMark regression on stoakley > disappears, but still has about 45% on tigerton. > > /me ponders a bit > > > > Does this make it any better? > I apply this patch and another one you sent on tbench email thread. > On stoakley, hackbench is recovered. If reverting the original 2 patches, > we get 8% improvement. > On tigerton, with your 2 patches, there is still about 45% regression. [ and here I got confused because this 45% seemed to match the 45% above, but then I saw it was hackbench vs volano ] > As for volanoMark, with your 2 patches, regression disappears on staokley > and it becomes about 35% on tigerton. So hackbench on tigerton is worse, but volano on tigerton is better with this patch vs reverting bits? > The good news is only tbench has about 6% regression on Nehalem machines. > Other regressions such like hackbench/aim7/volanoMark is not clear/big on > Nehalem. But reverting the original 2 patches don't fix the tbench regression > on Nehalem machines. Right, so Mike's suggestion of doing: echo NEXT_BUDDY > /debug/sched_features Seems like the next thing to try.. Mike, did we ever figure out _why_ NEXT_BUDDY introduced latencies? Buddies shouldn't make latencies worse than regular while(1); loops would.