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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,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 F1A87C37120 for ; Mon, 21 Jan 2019 21:35:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B358220861 for ; Mon, 21 Jan 2019 21:35:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="Jizh9qBr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728156AbfAUVfi (ORCPT ); Mon, 21 Jan 2019 16:35:38 -0500 Received: from mail.efficios.com ([167.114.142.138]:35144 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727580AbfAUVfi (ORCPT ); Mon, 21 Jan 2019 16:35:38 -0500 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 046D0B4FE9; Mon, 21 Jan 2019 16:35:36 -0500 (EST) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id jt5yF3_WzJu5; Mon, 21 Jan 2019 16:35:35 -0500 (EST) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 6663CB4FCD; Mon, 21 Jan 2019 16:35:35 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 6663CB4FCD DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1548106535; bh=emmEvvmvg4LpJ76voI4pvfqiprYl4MAXxEB0bZnS5JQ=; h=From:To:Date:Message-Id; b=Jizh9qBrya/Q0V864umhXR3X0rA2rEM5kNDJ3OwNfSQCHqxi9QF9i+Z5J8pTjDDUB gqoy12CgBmnnSb7Ux8D/7LFIvxbo7g68ZBYmAmmBhbhXVwWMphrFPyDyx0QTwcz8nf WQFxbmPWLb2tP545uqfRNwOuVnsjpvwZQjasZdFf7c2YBgCyWMsguiMeXz3LxsL4Ro /YZ6ydxjVt0LEgAAxvbNNURl7wCy12DYxgZxG15/4Mv2JVvz5bC5NY9tDRoIcQFImD ci2aKWaX039ObPA1shUO/smP0n//OfqBTeCPaHBR4fJJiYf2TYgTmiOQYJeKA+Lx6X EZneLj37YhuxA== 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 YKUJdvS9u63V; Mon, 21 Jan 2019 16:35:35 -0500 (EST) Received: from localhost.localdomain (192-222-157-41.qc.cable.ebox.net [192.222.157.41]) by mail.efficios.com (Postfix) with ESMTPSA id 0F53DB4FBD; Mon, 21 Jan 2019 16:35:35 -0500 (EST) 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: [RFC PATCH glibc 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Date: Mon, 21 Jan 2019 16:35:28 -0500 Message-Id: <20190121213530.23803-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190121213530.23803-1-mathieu.desnoyers@efficios.com> References: <20190121213530.23803-1-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 --- sysdeps/unix/sysv/linux/sched_getcpu.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c index b69eeda15c..37fda59d36 100644 --- a/sysdeps/unix/sysv/linux/sched_getcpu.c +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c @@ -24,8 +24,8 @@ #endif #include -int -sched_getcpu (void) +static int +vsyscall_sched_getcpu (void) { #ifdef __NR_getcpu unsigned int cpu; @@ -37,3 +37,24 @@ sched_getcpu (void) return -1; #endif } + +#ifdef __NR_rseq +#include + +extern __attribute__ ((tls_model ("initial-exec"))) +__thread volatile struct rseq __rseq_abi; + +int +sched_getcpu (void) +{ + int cpu_id = __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