From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C21D9C7EE25 for ; Wed, 7 Jun 2023 14:25:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241124AbjFGOZB (ORCPT ); Wed, 7 Jun 2023 10:25:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241129AbjFGOYx (ORCPT ); Wed, 7 Jun 2023 10:24:53 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99E2C1BF0 for ; Wed, 7 Jun 2023 07:24:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1686147885; x=1717683885; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=qOS33Z45j4TI2OKl5FBe0hF56pv3kMKz0o+IBc1D+4Q=; b=RpYTNEWfcZ2jZofeS5CMYpy5yn6+x2gEl8HsscDG+nmEN4B/5do9n+la SsRJYmxn1NmCkpJaN4nuD6Ltw9eMZ6QbWCeS+mTBMa4jz/5QJaZAfJ0h3 keAbUWsv7IOvd37aBF5GY8rw+91BJFwAj00VdAQzl4AGqeOSCWah/tcvu 9EBdMo770zMrdyZbP8qdZsVvM//V269TQjkgY2CNY9RKOcptV/3asqiyw zIgHLpEWlJYzFV6NnAFFioD/WHggfo3LZvWgdaUkHNO+wMMGR7hmlNQPW Dr4Gjqx2lqB1D/ThtXu7g6CinKMSHIaaLkq9DM/vMYS02FA5O66RAgY0N Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="337361334" X-IronPort-AV: E=Sophos;i="6.00,224,1681196400"; d="scan'208";a="337361334" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2023 07:23:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="659973610" X-IronPort-AV: E=Sophos;i="6.00,224,1681196400"; d="scan'208";a="659973610" Received: from linux-pnp-server-20.sh.intel.com ([10.239.146.185]) by orsmga003.jf.intel.com with ESMTP; 07 Jun 2023 07:23:23 -0700 From: Yu Ma To: yu.ma@intel.com Cc: Liam.Howlett@Oracle.com, akpm@linux-foundation.org, dan.j.williams@intel.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lipeng.zhu@intel.com, pan.deng@intel.com, shakeelb@google.com, tianyou.li@intel.com, tim.c.chen@intel.com, tim.c.chen@linux.intel.com Subject: [PATCH v2] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing Date: Wed, 7 Jun 2023 10:50:09 -0400 Message-Id: <20230607145009.58899-1-yu.ma@intel.com> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20230606125404.95256-1-yu.ma@intel.com> References: <20230606125404.95256-1-yu.ma@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running UnixBench/Execl throughput case, false sharing is observed due to frequent read on base_addr and write on free_bytes, chunk_md. UnixBench/Execl represents a class of workload where bash scripts are spawned frequently to do some short jobs. It will do system call on execl frequently, and execl will call mm_init to initialize mm_struct of the process. mm_init will call __percpu_counter_init for percpu_counters initialization. Then pcpu_alloc is called to read the base_addr of pcpu_chunk for memory allocation. Inside pcpu_alloc, it will call pcpu_alloc_area to allocate memory from a specified chunk. This function will update "free_bytes" and "chunk_md" to record the rest free bytes and other meta data for this chunk. Correspondingly, pcpu_free_area will also update these 2 members when free memory. Call trace from perf is as below: + 57.15% 0.01% execl [kernel.kallsyms] [k] __percpu_counter_init + 57.13% 0.91% execl [kernel.kallsyms] [k] pcpu_alloc - 55.27% 54.51% execl [kernel.kallsyms] [k] osq_lock - 53.54% 0x654278696e552f34 main __execve entry_SYSCALL_64_after_hwframe do_syscall_64 __x64_sys_execve do_execveat_common.isra.47 alloc_bprm mm_init __percpu_counter_init pcpu_alloc - __mutex_lock.isra.17 In current pcpu_chunk layout, ‘base_addr’ is in the same cache line with ‘free_bytes’ and ‘chunk_md’, and ‘base_addr’ is at the last 8 bytes. This patch moves ‘bound_map’ up to ‘base_addr’, to let ‘base_addr’ locate in a new cacheline. With this change, on Intel Sapphire Rapids 112C/224T platform, based on v6.4-rc4, the 160 parallel score improves by 24%. Reviewed-by: Tim Chen Signed-off-by: Yu Ma --- mm/percpu-internal.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index f9847c131998..ecc7be1ec876 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -41,10 +41,16 @@ struct pcpu_chunk { struct list_head list; /* linked to pcpu_slot lists */ int free_bytes; /* free bytes in the chunk */ struct pcpu_block_md chunk_md; + unsigned long *bound_map; /* boundary map */ + + /* + * To reduce false sharing, current layout is optimized to make sure + * base_addr locate in the different cacheline with free_bytes and + * chunk_md. + */ void *base_addr; /* base address of this chunk */ unsigned long *alloc_map; /* allocation map */ - unsigned long *bound_map; /* boundary map */ struct pcpu_block_md *md_blocks; /* metadata blocks */ void *data; /* chunk data */ -- 2.39.3