From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752689Ab2FKJ4l (ORCPT ); Mon, 11 Jun 2012 05:56:41 -0400 Received: from orion.tchmachines.com ([208.76.84.200]:44166 "EHLO orion.tchmachines.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751330Ab2FKJ4k (ORCPT ); Mon, 11 Jun 2012 05:56:40 -0400 From: Vlad Zolotarov To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ido Yariv , "Shai Fultheim (Shai@ScaleMP.com)" Subject: [PATCH v5 0/2] Move x86_cpu_to_apicid to the __read_mostly section Date: Mon, 11 Jun 2012 12:56:41 +0300 Message-ID: <2230701.XSbLcxrZ9Q@vlad> Organization: ScaleMP Ltd. User-Agent: KMail/4.8.3 (Linux/3.2.0-24-generic; KDE/4.8.3; i686; ; ) 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 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. More specifically, on vSMP Foundation platform x86_cpu_to_apicid shared the same internode_cache_line with frequently written lapic_events. >>From the analysis of the first 33 per_cpu variables out of 219 (memories they describe, to be more specific) the 8 have read_mostly nature (tlb_vector_offset, cpu_loops_per_jiffy, xen_debug_irq, etc.) and 25 are frequently written (irq_stack_union, gdt_page, exception_stacks, idt_desc, etc.). Assuming that the spread of the rest of the per_cpu variables is similar, identifying the read mostly memories will make more sense in terms of long-term code maintenance comparing to identifying frequently written memories. v5 changes: - Changed the description of the patch series and patch 2: added the analysis of the current per-cpu varibles spread between the read-mostly and frequently written groups. v4 changes: - Fixed the authors signatures in the patches. v3 changes: - Added the missing definitions of DEFINE_EARLY_PER_CPU_READ_MOSTLY() and DECLARE_EARLY_PER_CPU_READ_MOSTLY() macros in the !CONFIG_SMP code path in arch/x86/include/asm/percpu.h. thanks, vlad