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 308FEC7EE29 for ; Sat, 10 Jun 2023 02:40:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232637AbjFJCky (ORCPT ); Fri, 9 Jun 2023 22:40:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52116 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229606AbjFJCkw (ORCPT ); Fri, 9 Jun 2023 22:40:52 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDC892139 for ; Fri, 9 Jun 2023 19:40:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1686364850; x=1717900850; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=8jqWFsMfbwzSoZ5zFqaX3i8XF+2E5kDtejebv/Ye4BE=; b=RhgUI93DOudja0u48wnxJ8UwlRk6pclfA34FK2cPXgo8bS9lESdwPuQ1 YpfNNjGWuunLXb4BX6nlbvy4ppKgMf7pfJ0DwfdiPKi7qFf4vjoNRA5S4 rL6jIwzFvmluAtH3USBkkbgQMcy5IkyurRSNIe87RZnph0Iacuj9/93k9 DH+uJ8mFbvE1PwfrRJZdurAqCh0B/T5QlT7BUrVFhIAuGB24qKR0ND2Mb r//wqzM+CJCxOE4hKIvwumvO4sB+vnFi5wbhDEtpX4EECtOC7oryJpYX/ VdotuupSLg8xTcBuslTLlrJ8yQUQJ2uv+dZQrb28wNN9FSc9aPZmFYwTY Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="337361525" X-IronPort-AV: E=Sophos;i="6.00,231,1681196400"; d="scan'208";a="337361525" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jun 2023 19:40:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="854935287" X-IronPort-AV: E=Sophos;i="6.00,231,1681196400"; d="scan'208";a="854935287" Received: from linux-pnp-server-20.sh.intel.com ([10.239.146.185]) by fmsmga001.fm.intel.com with ESMTP; 09 Jun 2023 19:40:44 -0700 From: Yu Ma To: dennis@kernel.org, Liam.Howlett@oracle.com Cc: 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, yu.ma@intel.com Subject: [PATCH v3] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing Date: Fri, 9 Jun 2023 23:07:30 -0400 Message-Id: <20230610030730.110074-1-yu.ma@intel.com> X-Mailer: git-send-email 2.39.3 In-Reply-To: References: 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 | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index f9847c131998..7f108b25bb93 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -41,10 +41,17 @@ 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; - void *base_addr; /* base address of this chunk */ + unsigned long *bound_map; /* boundary map */ + + /* + * base_addr is the base address of this chunk. + * 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 ____cacheline_aligned_in_smp; 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