Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753995Ab0DZKDk (ORCPT ); Mon, 26 Apr 2010 06:03:40 -0400 Received: from hera.kernel.org ([140.211.167.34]:39079 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753450Ab0DZKDi (ORCPT ); Mon, 26 Apr 2010 06:03:38 -0400 Message-ID: <4BD564BE.6020700@kernel.org> Date: Mon, 26 Apr 2010 12:02:38 +0200 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: Pekka Enberg CC: "Zhang, Yanmin" , Christoph Lameter , "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Maciej Rutecki , Alex Shi , tim.c.chen@intel.com Subject: Re: [Bug #15713] hackbench regression due to commit 9dfc6e68bfe6e References: <4BD086D0.9090309@cs.helsinki.fi> <1272265147.2078.648.camel@ymzhang.sh.intel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Mon, 26 Apr 2010 10:02:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 964 Lines: 27 Hello, On 04/26/2010 09:22 AM, Pekka Enberg wrote: > On Mon, Apr 26, 2010 at 9:59 AM, Zhang, Yanmin > wrote: >>> I haven't been able to reproduce this either on my Core 2 machine. >> Mostly, the regression exists on Nehalem machines. I suspect it's related to >> hyper-threading machine. > > OK, so does anyone know why hyper-threading would change things for > the per-CPU allocator? My wild speculation is that previously the cpu_slub structures of two neighboring threads ended up on the same cacheline by accident thanks to the back to back allocation. W/ the percpu allocator, this no longer would happen as the allocator groups percpu data together per-cpu. Thanks. -- tejun -- 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/