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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 3E146C33CA9 for ; Mon, 13 Jan 2020 19:10:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AC4924655 for ; Mon, 13 Jan 2020 19:10:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729179AbgAMTKO (ORCPT ); Mon, 13 Jan 2020 14:10:14 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:40041 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728759AbgAMTKK (ORCPT ); Mon, 13 Jan 2020 14:10:10 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1ir55y-00019v-UA; Mon, 13 Jan 2020 20:09:51 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 1F9D31C18EE; Mon, 13 Jan 2020 20:09:32 +0100 (CET) Date: Mon, 13 Jan 2020 19:09:31 -0000 From: "tip-bot2 for Andrei Vagin" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: timers/core] lib/vdso: Add unlikely() hint into vdso_read_begin() Cc: Andrei Vagin , Dmitry Safonov , Thomas Gleixner , Vincenzo Frascino , x86 , LKML In-Reply-To: <20191112012724.250792-2-dima@arista.com> References: <20191112012724.250792-2-dima@arista.com> MIME-Version: 1.0 Message-ID: <157894257195.19145.2837202197610619244.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the timers/core branch of tip: Commit-ID: 79472606d6fba66c20299f4121a657ce73efc302 Gitweb: https://git.kernel.org/tip/79472606d6fba66c20299f4121a657ce73efc302 Author: Andrei Vagin AuthorDate: Tue, 12 Nov 2019 01:26:50 Committer: Thomas Gleixner CommitterDate: Mon, 13 Jan 2020 08:10:46 +01:00 lib/vdso: Add unlikely() hint into vdso_read_begin() Place the branch with no concurrent write before the 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 Co-developed-by: Dmitry Safonov Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov Signed-off-by: Thomas Gleixner Tested-by: Vincenzo Frascino Reviewed-by: Vincenzo Frascino Link: https://lore.kernel.org/r/20191112012724.250792-2-dima@arista.com --- include/vdso/helpers.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/vdso/helpers.h b/include/vdso/helpers.h index 01641db..9a2af9f 100644 --- a/include/vdso/helpers.h +++ b/include/vdso/helpers.h @@ -10,7 +10,7 @@ static __always_inline u32 vdso_read_begin(const struct vdso_data *vd) { u32 seq; - while ((seq = READ_ONCE(vd->seq)) & 1) + while (unlikely((seq = READ_ONCE(vd->seq)) & 1)) cpu_relax(); smp_rmb();