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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 328B2C46469 for ; Wed, 12 Sep 2018 14:18:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0C0D20839 for ; Wed, 12 Sep 2018 14:18:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D0C0D20839 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de 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 S1727063AbeILTXN (ORCPT ); Wed, 12 Sep 2018 15:23:13 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:43983 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726537AbeILTXN (ORCPT ); Wed, 12 Sep 2018 15:23:13 -0400 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1g05xO-0001pR-W6; Wed, 12 Sep 2018 16:17:27 +0200 Date: Wed, 12 Sep 2018 16:17:26 +0200 (CEST) From: Thomas Gleixner To: Florian Weimer cc: Andy Lutomirski , Matt Rickard , Stephen Boyd , John Stultz , X86 ML , LKML Subject: Re: [PATCH v3] x86/vdso: Handle clock_gettime(CLOCK_TAI) in vDSO In-Reply-To: Message-ID: References: <20180901015935.CCF0B18E20A9@virtux64.softrans.com.au> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 12 Sep 2018, Florian Weimer wrote: > On 09/09/2018 10:05 PM, Thomas Gleixner wrote: > > See the patch below. It's integrating TAI without slowing down everything > > and it definitely does not result in indirect calls. > > > > On a HSW it slows down clock_gettime() by ~0.5ns. On a SKL I get a speedup > > by ~0.5ns. On a AMD Epyc server it's 1.2ns speedup. So it somehow depends > > on the uarch and I also observed compiler version dependend variations. > > Does this mean glibc can keep using a single vDSO entrypoint, the one we > have today? We have no intention to change that. But we surely could provide separate entry points as an extra to avoid a bunch of conditionals. Thanks, tglx