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 BB922C77B74 for ; Tue, 11 Apr 2023 13:43:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230135AbjDKNnn (ORCPT ); Tue, 11 Apr 2023 09:43:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58142 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230031AbjDKNnm (ORCPT ); Tue, 11 Apr 2023 09:43:42 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB2661707; Tue, 11 Apr 2023 06:43:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1681220621; x=1712756621; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=2GeQQq+KcbTCEU+rXh5JGw+yLkL8a8JmHupdRnaoc8M=; b=chh0jmd4I6VNBC14A5780CVuHTxHv34bO0UjY1fWhG0r+A/g9vuNnnrk E+fR5m5J7LjjjauKWjtM5cDvn/VshNJS7PkdCiRCVmTIhUshEwoVGEG8b wy1Pi7MzUi65BzAmzI0VR+9oQ7q8s3WT3M0V1L5tNCwwunJzcv97RHTzx 8Qq1eRnZKzEXBwkocoGx0q2IWHtWIVYVgI46XPRMqoq1DfPfa0JUw94/i wfzMjpmAHVtA+0eunF8M3nQVkiQyBB+wHFH9lRuec31hAZeGU7Aky1Osl AO673s42/mPq2YqPWCRbRKBnog/LYpIYyM7jKV5gjF4yHdc6en+zZzG0n w==; X-IronPort-AV: E=McAfee;i="6600,9927,10677"; a="429905385" X-IronPort-AV: E=Sophos;i="5.98,336,1673942400"; d="scan'208";a="429905385" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2023 06:43:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10677"; a="812566489" X-IronPort-AV: E=Sophos;i="5.98,336,1673942400"; d="scan'208";a="812566489" Received: from gtryonx-mobl.amr.corp.intel.com (HELO [10.209.72.81]) ([10.209.72.81]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2023 06:43:39 -0700 Message-ID: <1fee0372-3a3b-5e09-38c3-ffb3523fe195@intel.com> Date: Tue, 11 Apr 2023 06:43:39 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v2 0/5] locking: Introduce local{,64}_try_cmpxchg Content-Language: en-US To: Mark Rutland Cc: Uros Bizjak , linux-alpha@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Arnd Bergmann , Peter Zijlstra , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Will Deacon , Boqun Feng , Jiaxun Yang , Jun Yi References: <20230405141710.3551-1-ubizjak@gmail.com> <7360ffd2-a5aa-1373-8309-93e71ff36cbb@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On 4/11/23 04:35, Mark Rutland wrote: > I agree it'd be nice to have performance figures, but I think those would only > need to demonstrate a lack of a regression rather than a performance > improvement, and I think it's fairly clear from eyeballing the generated > instructions that a regression isn't likely. Thanks for the additional context. I totally agree that there's zero burden here to show a performance increase. If anyone can think of a quick way to do _some_ kind of benchmark on the code being changed and just show that it's free of brown paper bags, it would be appreciated. Nothing crazy, just think of one workload (synthetic or not) that will stress the paths being changed and run it with and without these changes. Make sure there are not surprises. I also agree that it's unlikely to be brown paper bag material.