From patchwork Fri Jun 14 15:23:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Desnoyers X-Patchwork-Id: 1116069 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=sourceware.org (client-ip=209.132.180.131; helo=sourceware.org; envelope-from=libc-alpha-return-102730-incoming=patchwork.ozlabs.org@sourceware.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.b="umEgTB0/"; dkim=pass (2048-bit key; unprotected) header.d=efficios.com header.i=@efficios.com header.b="ZxhHLReM"; dkim-atps=neutral Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45QPWq5gjhz9s3l for ; Sat, 15 Jun 2019 01:23:35 +1000 (AEST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id:in-reply-to :references; q=dns; s=default; b=Y+Rw0yMZLTdBlb7H0wODu6314BoLFs0 jXnp1Y6lSyOqprP/HlbTKO+yWhkQ/A4BqsxLxdihcwELfv/EfcoFoKhzbZcjbRIH aP4UYI8OlQQK7tZxxFc0QgOGtjuK7wtuq9ZKeb7kwQDDfa2gb+1MgB+xyDuA0zPO 6s6EIf+HGkYc= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id:in-reply-to :references; s=default; bh=W0pXSE/cXuTqUNQ0Uw+gKIeCHyU=; b=umEgT B0/i379JXTw8w/X3wvDCM7jmw40dkyQPahgAkxoT0FQPMDAcnNnjqQFkDJVsAC+v zHKUe4Ha4ML2ZQ4Uxy2g1hnuZ71VBvc7fni2FP52xcc8jmK0DafMip1RMUznkdBn /7gVnFcEMintoaMxDWIO52Mrxl1z7epT99RRk8= Received: (qmail 102148 invoked by alias); 14 Jun 2019 15:23:15 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 102056 invoked by uid 89); 14 Jun 2019 15:23:14 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-24.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.1 spammy=08, 0.8, 3823 X-HELO: mail.efficios.com 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== 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> In-Reply-To: <20190614152304.12321-1-mathieu.desnoyers@efficios.com> References: <20190614152304.12321-1-mathieu.desnoyers@efficios.com> 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