From patchwork Tue Feb 12 19:42:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Desnoyers X-Patchwork-Id: 1040806 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-99979-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="isVm/VvQ"; dkim=pass (2048-bit key; unprotected) header.d=efficios.com header.i=@efficios.com header.b="Li0mLark"; 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 43zY473bS0z9s4Z for ; Wed, 13 Feb 2019 06:43:35 +1100 (AEDT) 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=oOhZAU7kNPaBGDSOlpBx4OHyEdhcJMl /VLdlbJDKHI6thp+8d/QKu3KOCjDZkRoem8a/AxAqwm5zlG+xlAplDFXNe5oung7 gbuBhva+mdqvvy10dte6goNOGAVfz5QLfH1zv4ZAQ8JgLa+4B7Lq2CukGdcFeJ7o WIlEbeg+r6tU= 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=1tVaEFrkKXYWcTWS19bblfXJQLU=; b=isVm/ VvQTU5ld0Y1inqfnhPhcZV2DSDLZmN0ohUXgmzmVSP/nQAsT5ysDtZQ+JV7vNFqa TK5jKkcyWcXmNjstKtna97I3XvzmEAaW6MS/t4wZu7NOBRR8qo4HFuw/5mtfEMED UPLq/YKSZoDYchHcazpbEs/Drvz2RI3ZVV5H08= Received: (qmail 59072 invoked by alias); 12 Feb 2019 19:43:13 -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 58998 invoked by uid 89); 12 Feb 2019 19:43:13 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy=0.8, HDKIM-Filter:v2.10.3, __thread, Feng X-HELO: mail.efficios.com DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com E04E21A1AFF DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1550000589; bh=AWYbTmbbUu9whfET+jatobpOKB+ZZRz448Bik1cpDV0=; h=From:To:Date:Message-Id; b=Li0mLarkExrbEuurvDqnwcBnczDCJsAjyQMUiJ2vOiXPVanOiQ51nhdi4I6gxyzoj VtiTKYDxMRN/uGT2fLR8xt/7BLgbaVBZuXtdnLocaqcC0RLxWPy03E26fC0E8ljNeE pjlC9oDWEx54El2mDh5PB9Vxr1angPTVgyabDd0NQkte6hemd9fkQXDUOvr7tMuVNH i9pPFFAbJwxjNMmDBFRsKHYCZivGXSChQgbfpkug+tKuGmmvXhnwGwM7QScYCnwfHR SQ+x3MPlWXVXj0WcUMXiIk5XDRM4vm4OQTRL3yDs4fvjYAJOxg6zby5X1NOsjHRrxy rgpXpNiHSo1Gg== 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 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Date: Tue, 12 Feb 2019 14:42:51 -0500 Message-Id: <20190212194253.1951-3-mathieu.desnoyers@efficios.com> In-Reply-To: <20190212194253.1951-1-mathieu.desnoyers@efficios.com> References: <20190212194253.1951-1-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 Reviewed-by: Carlos O'Donell --- 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 fb0d317f83..8bfb03778b 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