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=-10.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E3479CA9EAF for ; Thu, 24 Oct 2019 09:28:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF3462166E for ; Thu, 24 Oct 2019 09:28:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438538AbfJXJ2h (ORCPT ); Thu, 24 Oct 2019 05:28:37 -0400 Received: from foss.arm.com ([217.140.110.172]:44064 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732234AbfJXJ2h (ORCPT ); Thu, 24 Oct 2019 05:28:37 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4E10B31F; Thu, 24 Oct 2019 02:28:23 -0700 (PDT) Received: from [10.37.9.200] (unknown [10.37.9.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EC5843F718; Thu, 24 Oct 2019 02:28:15 -0700 (PDT) Subject: Re: [PATCHv7 18/33] lib/vdso: Add unlikely() hint into vdso_read_begin() To: Andrei Vagin Cc: Dmitry Safonov , linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Adrian Reber , Andrei Vagin , Andy Lutomirski , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org References: <20191011012341.846266-1-dima@arista.com> <20191011012341.846266-19-dima@arista.com> <100f6921-9081-7eb0-7acc-f10cfb647c21@arm.com> <20191024061311.GA4541@gmail.com> From: Vincenzo Frascino Message-ID: <9aa9857e-ee1c-0117-bfcb-45fc6bcab866@arm.com> Date: Thu, 24 Oct 2019 10:30:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191024061311.GA4541@gmail.com> Content-Type: text/plain; charset=koi8-r Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrei, On 10/24/19 7:13 AM, Andrei Vagin wrote: > On Wed, Oct 16, 2019 at 12:24:14PM +0100, Vincenzo Frascino wrote: >> On 10/11/19 2:23 AM, Dmitry Safonov wrote: >>> From: Andrei Vagin >>> >>> Place the branch with no concurrent write before contended case. >>> >>> Performance numbers for Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz >>> (more clock_gettime() cycles - the better): >>> | before | after >>> ----------------------------------- >>> | 150252214 | 153242367 >>> | 150301112 | 153324800 >>> | 150392773 | 153125401 >>> | 150373957 | 153399355 >>> | 150303157 | 153489417 >>> | 150365237 | 153494270 >>> ----------------------------------- >>> avg | 150331408 | 153345935 >>> diff % | 2 | 0 >>> ----------------------------------- >>> stdev % | 0.3 | 0.1 >>> >>> Signed-off-by: Andrei Vagin >>> Co-developed-by: Dmitry Safonov >>> Signed-off-by: Dmitry Safonov >> >> Reviewed-by: Vincenzo Frascino >> Tested-by: Vincenzo Frascino > > Hello Vincenzo, > > Could you test the attached patch on aarch64? On x86, it gives about 9% > performance improvement for CLOCK_MONOTONIC and CLOCK_BOOTTIME. > I did run similar tests in past with a previous version of the unified vDSO library and what I can tell based on the results of those is that the impact of "__always_inline" alone was around 7% on arm64, in fact I had a comment stating "To improve performances, in this file, __always_inline it is used for the functions called multiple times." in my implementation [1]. [1] https://bit.ly/2W9zMxB I spent some time yesterday trying to dig out why the approach did not make the cut but I could not infer it from the review process. > Here is my test: > https://github.com/avagin/vdso-perf > > It is calling clock_gettime() in a loop for three seconds and then > reports a number of iterations. > I am happy to run the test on arm64 and provide some results. > Thanks, > Andrei > -- Regards, Vincenzo