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 CD39DC4646A for ; Wed, 12 Sep 2018 13:01:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CFDE20882 for ; Wed, 12 Sep 2018 13:01:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8CFDE20882 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1727007AbeILSGL (ORCPT ); Wed, 12 Sep 2018 14:06:11 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55002 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726491AbeILSGK (ORCPT ); Wed, 12 Sep 2018 14:06:10 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AA61740216FE; Wed, 12 Sep 2018 13:01:45 +0000 (UTC) Received: from oldenburg.str.redhat.com (dhcp-192-212.str.redhat.com [10.33.192.212]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3C4532166BA3; Wed, 12 Sep 2018 13:01:44 +0000 (UTC) Subject: Re: [PATCH v3] x86/vdso: Handle clock_gettime(CLOCK_TAI) in vDSO To: Thomas Gleixner , Andy Lutomirski Cc: Matt Rickard , Stephen Boyd , John Stultz , X86 ML , LKML References: <20180901015935.CCF0B18E20A9@virtux64.softrans.com.au> From: Florian Weimer Message-ID: Date: Wed, 12 Sep 2018 15:01:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 12 Sep 2018 13:01:45 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 12 Sep 2018 13:01:45 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'fweimer@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Thanks, Florian