Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759216AbZABSzo (ORCPT ); Fri, 2 Jan 2009 13:55:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757629AbZABSzf (ORCPT ); Fri, 2 Jan 2009 13:55:35 -0500 Received: from byss.tchmachines.com ([208.76.80.75]:54700 "EHLO byss.tchmachines.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757500AbZABSzf (ORCPT ); Fri, 2 Jan 2009 13:55:35 -0500 Date: Fri, 2 Jan 2009 10:55:24 -0800 From: Ravikiran G Thirumalai To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, travis@sgi.com, stable@kernel.org, shai@scalex86.org Subject: Re: [patch] x86: Fix incorrect __read_mostly on _boot_cpu_pda Message-ID: <20090102185524.GB6856@localdomain> References: <20081231214446.GA6856@localdomain> <20090102160949.GF1180@elte.hu> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="p2kqVDKq5asng8Dg" Content-Disposition: inline In-Reply-To: <20090102160949.GF1180@elte.hu> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - byss.tchmachines.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - scalex86.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2396 Lines: 72 --p2kqVDKq5asng8Dg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jan 02, 2009 at 05:09:51PM +0100, Ingo Molnar wrote: > >* Ravikiran G Thirumalai wrote: > >> The pda rework (commit 3461b0af025251bbc6b3d56c821c6ac2de6f7209) >> to remove static boot cpu pdas introduced a bug. _boot_cpu_pda is the >> actual pda used by the boot cpu and is definitely not "__read_mostly" and >> ended up polluting the read mostly section with writes. This bug caused >> regression of about 8-10% on certain syscall intensive workloads. >> >> Signed-off-by: Ravikiran Thirumalai > >applied to tip/x86/urgent, with a Cc: stable tag. Thanks, > Thanks! Stable maintainers, please consider this for 2.6.27 stable as well (in addition to 28). (Attaching the tip/x86/urgent commit as reference to the patch) Thanks, Kiran --p2kqVDKq5asng8Dg Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename=fix_incorrect_readmostly commit 26799a63110dcbe81291ea53178f6b4810d07424 Author: Ravikiran G Thirumalai Date: Wed Dec 31 13:44:46 2008 -0800 x86: fix incorrect __read_mostly on _boot_cpu_pda The pda rework (commit 3461b0af025251bbc6b3d56c821c6ac2de6f7209) to remove static boot cpu pdas introduced a performance bug. _boot_cpu_pda is the actual pda used by the boot cpu and is definitely not "__read_mostly" and ended up polluting the read mostly section with writes. This bug caused regression of about 8-10% on certain syscall intensive workloads. Signed-off-by: Ravikiran Thirumalai Acked-by: Mike Travis Cc: Signed-off-by: Ingo Molnar diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 388e05a..b9a4d8c 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -27,7 +27,7 @@ #include /* boot cpu pda */ -static struct x8664_pda _boot_cpu_pda __read_mostly; +static struct x8664_pda _boot_cpu_pda; #ifdef CONFIG_SMP /* --p2kqVDKq5asng8Dg-- -- 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/