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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 3DC5CC31E4B for ; Fri, 14 Jun 2019 15:23:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2F6321744 for ; Fri, 14 Jun 2019 15:23:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="ZxhHLReM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726297AbfFNPXM (ORCPT ); Fri, 14 Jun 2019 11:23:12 -0400 Received: from mail.efficios.com ([167.114.142.138]:49952 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726083AbfFNPXM (ORCPT ); Fri, 14 Jun 2019 11:23:12 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id EEC6825174D; Fri, 14 Jun 2019 11:23:10 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id dHBNh9EPKqVL; Fri, 14 Jun 2019 11:23:10 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id AA480251731; Fri, 14 Jun 2019 11:23:08 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com AA480251731 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1560525788; bh=OBox3OMxjxvC7PvoLYGWSN3dsx6DMeQHxfzI7UPjj1Y=; h=From:To:Date:Message-Id; b=ZxhHLReM1LIW1i4jvG82L8qd3m5LTPJDyXwDqty0mpFQ+PLM8Cp+W8h7rbu734ot7 1Qg6PIsk3Q7eYwHmQEuH3mqUrMoYcqExVUsVlkB3ehCCcSSj7BDPSoHhGE61e2qXk3 1YWyu18xdbqY6QiRcvEfvoUpuZdvaZbNux0oI2PFtFfshhaSZpXcDfNkqsBbeK04Cq zFNu2khFa6v4rXfjX3jNPBAsvjO1NCOPjV8OeL6X7WoPzKrpW4fPeJoYBiCx1OS0uq L6HiXqZWIgOHjhdQXVDEhVs55OyLIH9rME6OctJDlrefUJQcZnehuOQ6ABHcrRk6fa g3yhiwSdJrUyg== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id Uimi5a9qPjeK; Fri, 14 Jun 2019 11:23:08 -0400 (EDT) Received: from localhost.localdomain (192-222-181-218.qc.cable.ebox.net [192.222.181.218]) by mail.efficios.com (Postfix) with ESMTPSA id 655E725171F; Fri, 14 Jun 2019 11:23:08 -0400 (EDT) From: Mathieu Desnoyers To: Carlos O'Donell Cc: Florian Weimer , Joseph Myers , Szabolcs Nagy , libc-alpha@sourceware.org, Mathieu Desnoyers , Thomas Gleixner , Ben Maurer , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Will Deacon , Dave Watson , Paul Turner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH glibc 2/5] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux (v5) Date: Fri, 14 Jun 2019 11:23:01 -0400 Message-Id: <20190614152304.12321-3-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190614152304.12321-1-mathieu.desnoyers@efficios.com> References: <20190614152304.12321-1-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When available, use the cpu_id field from __rseq_abi on Linux to implement sched_getcpu(). Fall-back on the vgetcpu vDSO if unavailable. Benchmarks: x86-64: Intel E5-2630 v3@2.40GHz, 16-core, hyperthreading glibc sched_getcpu(): 13.7 ns (baseline) glibc sched_getcpu() using rseq: 2.5 ns (speedup: 5.5x) inline load cpuid from __rseq_abi TLS: 0.8 ns (speedup: 17.1x) Signed-off-by: Mathieu Desnoyers CC: Carlos O'Donell CC: Florian Weimer CC: Joseph Myers CC: Szabolcs Nagy CC: Thomas Gleixner CC: Ben Maurer CC: Peter Zijlstra CC: "Paul E. McKenney" CC: Boqun Feng CC: Will Deacon CC: Dave Watson CC: Paul Turner CC: libc-alpha@sourceware.org CC: linux-kernel@vger.kernel.org CC: linux-api@vger.kernel.org --- Changes since v1: - rseq is only used if both __NR_rseq and RSEQ_SIG are defined. Changes since v2: - remove duplicated __rseq_abi extern declaration. Changes since v3: - update ChangeLog. Changes since v4: - Use atomic_load_relaxed to load the __rseq_abi.cpu_id field, a consequence of the fact that __rseq_abi is not volatile anymore. - Include atomic.h which provides atomic_load_relaxed. --- ChangeLog | 5 +++++ sysdeps/unix/sysv/linux/sched_getcpu.c | 25 +++++++++++++++++++++++-- 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index 01a411acbf..58830cafc2 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2019-04-23 Mathieu Desnoyers + + * sysdeps/unix/sysv/linux/sched_getcpu.c: use rseq cpu_id TLS on + Linux. + 2019-04-23 Mathieu Desnoyers * NEWS: Add Restartable Sequences feature description. diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c index fb0d317f83..01a818f5b0 100644 --- a/sysdeps/unix/sysv/linux/sched_getcpu.c +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c @@ -18,14 +18,15 @@ #include #include #include +#include #ifdef HAVE_GETCPU_VSYSCALL # define HAVE_VSYSCALL #endif #include -int -sched_getcpu (void) +static int +vsyscall_sched_getcpu (void) { #ifdef __NR_getcpu unsigned int cpu; @@ -37,3 +38,23 @@ sched_getcpu (void) return -1; #endif } + +#ifdef __NR_rseq +#include +#endif + +#if defined __NR_rseq && defined RSEQ_SIG +int +sched_getcpu (void) +{ + int cpu_id = atomic_load_relaxed (&__rseq_abi.cpu_id); + + return cpu_id >= 0 ? cpu_id : vsyscall_sched_getcpu (); +} +#else +int +sched_getcpu (void) +{ + return vsyscall_sched_getcpu (); +} +#endif -- 2.17.1