From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754987Ab2EUPmY (ORCPT ); Mon, 21 May 2012 11:42:24 -0400 Received: from orion.tchmachines.com ([208.76.84.200]:60294 "EHLO orion.tchmachines.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754690Ab2EUPmW (ORCPT ); Mon, 21 May 2012 11:42:22 -0400 From: Vlad Zolotarov To: Ingo Molnar Cc: "H. Peter Anvin" , Thomas Gleixner , linux-kernel , Shai@scalemp.com, ido@wizery.com Subject: Re: [PATCH v4 0/2] Move x86_cpu_to_apicid to the __read_mostly section Date: Mon, 21 May 2012 18:42:18 +0300 Message-ID: <1918812.66k1TLBkOr@vlad> Organization: ScaleMP Ltd. User-Agent: KMail/4.8.2 (Linux/3.2.0-24-generic; KDE/4.8.2; i686; ; ) In-Reply-To: <20120521152345.GC7068@gmail.com> References: <1744141.b5asW8k6jC@vlad> <20120521152345.GC7068@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - orion.tchmachines.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - scalemp.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, May 21, 2012 17:23:48 Ingo Molnar wrote: > * Vlad Zolotarov wrote: > > Pls., consider applying this patch series. > > > > It contains the following changes: > > - Adds two new macros DEFINE_EARLY_PER_CPU_READ_MOSTLY() and > > > > DECLARE_EARLY_PER_CPU_READ_MOSTLY(). > > > > - Adds "read-mostly" qualifier to the following variables in smp.h: > > - cpu_sibling_map > > - cpu_core_map > > - cpu_llc_shared_map > > - cpu_llc_id > > - cpu_number > > - x86_cpu_to_apicid > > - x86_bios_cpu_apicid > > - x86_cpu_to_logical_apicid > > > > As long as all the variables above are only written during the > > initialization, this change is meant to prevent the false > > sharing and improve the performance on large multiprocessor > > systems. > > Why have you resent this? The feedback I gave has not been > > addressed: Hmmm... I'm a bit confused. There were two feedbacks/threads: one on "Signed- off-by" format and the other where u asked for a justification on a vSMP side. The signed-off format sounded to me as a clear blocker for a series so I fixed it and respined. I also mentioned it in patch0. The second thread seams like getting to submitting a separate patch with a doc under Documents and vSMP testing results explaining and justifying when and were per-CPU and/or __read_mostly variables should be used. Pls., correct me if I misunderstood u and let me know what should I do next in order to make this patch series accepted. thanks, vlad > > Well, a quick tally of percpu variables on a 'make defconfig' > > kernel would tell us one way or another? > > > > Here there's almost 200 percpu variables active in the 64-bit > > x86 defconfig, and a quick random sample suggests that most > > are read-mostly. > > > > I have no fundamental prefer to either approach, but the > > direction taken should be justified explicitly, with numbers, > > arguments, etc. - also a short blurb somewhere in the headers > > that explains when they should be used, so that others can be > > aware of vSMP's special needs here. > > Thanks, > > Ingo