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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD45BC433E7 for ; Tue, 13 Oct 2020 23:48:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AD4021D7A for ; Tue, 13 Oct 2020 23:48:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602632923; bh=8/PBWQgz3SSTYl6EQciCTEV/iX++FB+zToIPRNXfJj4=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=DSoRD9VBQmHDsyYq3d+HOIQ9QFvtG1gz/ICwTW6hegEZx4HHpXrE0a6CwXsiD3PU6 GcoiE/fxy8N7LqC7jJtBkxKOpqVS4PkUI7E8yOiK0XgVAyvoI45wghq1FUzaJPvlYM HQEltSW8+obMwdx3plYTvHIH5XvQMHsAgw7sYKRw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727356AbgJMXsn (ORCPT ); Tue, 13 Oct 2020 19:48:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:60174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727154AbgJMXsn (ORCPT ); Tue, 13 Oct 2020 19:48:43 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DD10F21582; Tue, 13 Oct 2020 23:48:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602632921; bh=8/PBWQgz3SSTYl6EQciCTEV/iX++FB+zToIPRNXfJj4=; h=Date:From:To:Subject:In-Reply-To:From; b=ScSdMgNvvSGYQINmsduZUSwXq2LiCM1DxiVUR+1Sbkrvjm+DRQ1GK3QTC6peL+I/9 5O+tfOTkJ2Pl6SErZtwU6a3c1IVjS3Qi/hkJGiEUVYFvpvdaxJ9lAO6CYC/VeukqGa URai/M8vAvnSs52zcfsvLorQMTB56tvO0aqoD8Xo= Date: Tue, 13 Oct 2020 16:48:40 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cl@linux.com, hewenliang4@huawei.com, hushiyuan@huawei.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, penberg@kernel.org, rientjes@google.com, torvalds@linux-foundation.org, wuyun.wu@huawei.com Subject: [patch 021/181] mm/slub.c: branch optimization in free slowpath Message-ID: <20201013234840.43ZfRzqi3%akpm@linux-foundation.org> In-Reply-To: <20201013164658.3bfd96cc224d8923e66a9f4e@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Abel Wu Subject: mm/slub.c: branch optimization in free slowpath The two conditions are mutually exclusive and gcc compiler will optimise this into if-else-like pattern. Given that the majority of free_slowpath is free_frozen, let's provide some hint to the compilers. Tests (perf bench sched messaging -g 20 -l 400000, executed 10x after reboot) are done and the summarized result: un-patched patched max. 192.316 189.851 min. 187.267 186.252 avg. 189.154 188.086 stdev. 1.37 0.99 Link: http://lkml.kernel.org/r/20200813101812.1617-1-wuyun.wu@huawei.com Signed-off-by: Abel Wu Acked-by: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Hewenliang Cc: Hu Shiyuan Signed-off-by: Andrew Morton --- mm/slub.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) --- a/mm/slub.c~mm-slub-branch-optimization-in-free-slowpath +++ a/mm/slub.c @@ -3019,20 +3019,21 @@ static void __slab_free(struct kmem_cach if (likely(!n)) { - /* - * If we just froze the page then put it onto the - * per cpu partial list. - */ - if (new.frozen && !was_frozen) { + if (likely(was_frozen)) { + /* + * The list lock was not taken therefore no list + * activity can be necessary. + */ + stat(s, FREE_FROZEN); + } else if (new.frozen) { + /* + * If we just froze the page then put it onto the + * per cpu partial list. + */ put_cpu_partial(s, page, 1); stat(s, CPU_PARTIAL_FREE); } - /* - * The list lock was not taken therefore no list - * activity can be necessary. - */ - if (was_frozen) - stat(s, FREE_FROZEN); + return; } _