From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 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 dcvr.yhbt.net (Postfix) with ESMTPS id E769C211B4 for ; Tue, 4 Dec 2018 19:22:12 +0000 (UTC) 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=KY6cN/kT9AXe2VrYv0sQuZVSPjF/S07 7idN7L7wF87DjkiBss2AqWo7Y7i5JNBiXqIlnSvfxhWVSa2ZS0xT94uafF4A7+V9 2LIKBx9+dLPUtz81yn9Zu5ip6y4v7eRbBJMlXFFBVAh54dwW8yl/x6dsJn/FUfIC k3bwCtJqioPE= 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=HQ/R83LY+Mf40KjdjvKHMYaQd+o=; b=iMqqg SPY7TLrKQ2yTh79YWdFnKK8SB03bKhWZEJvBU1fKv/4WA8405wajK6T/D9x8SGC+ 0PQMGZeaXxWcaItGNe8dNRhmawksPQLtLpZ/JuADoohscqf+safx30ZqiH0SevKD 8zjVXj/MtTbAYE8HsaAsBW3wfaqhpYI14J8hVA= Received: (qmail 3016 invoked by alias); 4 Dec 2018 19:22:01 -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 Received: (qmail 2945 invoked by uid 89); 4 Dec 2018 19:22:01 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: mail.efficios.com DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 14F6D9E50F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1543951316; bh=emmEvvmvg4LpJ76voI4pvfqiprYl4MAXxEB0bZnS5JQ=; h=From:To:Date:Message-Id; b=IOYy0yXGSuOIzVvzCDlLiGd/QbJlrZh/zYReiOmzMC7TTD8jSRx1lwHA2TY61QEdl HuyIYtOGfuyrzaEL2DhcrWHziwST81GrbrFqb9KH1/kYdUMjdG+fYENILklN252LwS J9eieTJW83UJf43ZkoDyHw33+jooTWl7Oj8qd9FlfRvobXA1VzsgCjC8X3IDbq/52c VeZAZe8IyAYlAWzfFu/aPVzeQAY3Y8ok2v2UDH1cEXjtTO/ewy2gRCRi+aso1ySYD3 KyDT1CKUc/lh6SU+KDSKhp8bxMplmbSv8rWnI399wS2SywnQxcacHOnqGpSzNHzy8Q lX8zFXWEddk/Q== 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: Tue, 4 Dec 2018 14:21:39 -0500 Message-Id: <20181204192141.4684-2-mathieu.desnoyers@efficios.com> In-Reply-To: <20181204192141.4684-1-mathieu.desnoyers@efficios.com> References: <20181204192141.4684-1-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 --- 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