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_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 CDB58C32789 for ; Fri, 2 Nov 2018 11:53:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6379C20657 for ; Fri, 2 Nov 2018 11:53:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="ZZSYwnaW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6379C20657 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726821AbeKBVAE (ORCPT ); Fri, 2 Nov 2018 17:00:04 -0400 Received: from mail.efficios.com ([167.114.142.138]:45244 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbeKBVAD (ORCPT ); Fri, 2 Nov 2018 17:00:03 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id E64732488C0; Fri, 2 Nov 2018 07:53:06 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id skhbbq-SB2sz; Fri, 2 Nov 2018 07:53:06 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 94FA52488BB; Fri, 2 Nov 2018 07:53:06 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 94FA52488BB DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1541159586; bh=ARIXVDaQRUZ7X2dcuyortmQVt+ZsZwR9tFSZPo3/9TE=; h=From:To:Date:Message-Id; b=ZZSYwnaWvaHeKXt1fPCsxFWd4tkBzWSXDVX2O5uWZ/j5MuURmLQG4GBpLDoOUVmxB tHmhi9imrNCjYMmvtsKWDy69aD3p4bSDk8EiXgqK34Oztt/FrE3nferm9K9BA6v4Rl Z8+cst2yRmsOjTnPwWBgQ7WOFsZTW/ssXzJsZr9gd/8yKDu0fICERrSJFUtBntZaDu QzRMaM6XZJnMSXIsSzVrZRIwTYhF/SV/JweutFJgVIxLkyUrTdM+XdAfU6BLTzBfVN ELSuMv5ldHA8ms7AHygqxqKNrQrGQeVs6UOhDb68mgHqhJ6HxKATh/yKRRnn9wjTHx j3/WmM1Hd+mrw== 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 r582tG_CYFPt; Fri, 2 Nov 2018 07:53:06 -0400 (EDT) Received: from localhost.localdomain (192-222-157-41.qc.cable.ebox.net [192.222.157.41]) by mail.efficios.com (Postfix) with ESMTPSA id 4EA4B2488AF; Fri, 2 Nov 2018 07:53:06 -0400 (EDT) From: Mathieu Desnoyers To: libc-alpha@sourceware.org Cc: Mathieu Desnoyers , Carlos O'Donell , Florian Weimer , Joseph Myers , Szabolcs Nagy , 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 2/2] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Date: Fri, 2 Nov 2018 07:52:59 -0400 Message-Id: <20181102115259.11383-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181102115259.11383-1-mathieu.desnoyers@efficios.com> References: <20181102115259.11383-1-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..e1a206075c 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