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_HELO_NONE,SPF_PASS autolearn=unavailable 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 C6EC0C48BE9 for ; Mon, 24 Jun 2019 12:51:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7E58213F2 for ; Mon, 24 Jun 2019 12:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728378AbfFXMvC (ORCPT ); Mon, 24 Jun 2019 08:51:02 -0400 Received: from foss.arm.com ([217.140.110.172]:49274 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727965AbfFXMvC (ORCPT ); Mon, 24 Jun 2019 08:51:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F20E7344; Mon, 24 Jun 2019 05:51:00 -0700 (PDT) Received: from donnerap.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7EDFB3F718; Mon, 24 Jun 2019 05:50:58 -0700 (PDT) Date: Mon, 24 Jun 2019 13:50:55 +0100 From: Andre Przywara To: Vincenzo Frascino Cc: , , , , , Catalin Marinas , Will Deacon , Arnd Bergmann , Russell King , Ralf Baechle , Paul Burton , Daniel Lezcano , Thomas Gleixner , Mark Salyzyn , Peter Collingbourne , Shuah Khan , Dmitry Safonov <0x7f454c46@gmail.com>, Rasmus Villemoes , Huw Davies , Shijith Thotton Subject: Re: [PATCH v7 00/25] Unify vDSOs across more architectures Message-ID: <20190624135055.7020fc2a@donnerap.cambridge.arm.com> In-Reply-To: <20190621095252.32307-1-vincenzo.frascino@arm.com> References: <20190621095252.32307-1-vincenzo.frascino@arm.com> Organization: ARM X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; aarch64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Fri, 21 Jun 2019 10:52:27 +0100 Vincenzo Frascino wrote: Hi, > vDSO (virtual dynamic shared object) is a mechanism that the Linux > kernel provides as an alternative to system calls to reduce where > possible the costs in terms of cycles. [ ... ] Some numbers for the ARM(32) part: I booted my trusted old Calxeda Midway server (Cortex A-15 cores) and ran the vdsotest benchmark on it. The results are: (vdso: times, in nsec/call; n/t: "not tested" (=not implemented)) call 5.2-rc3 5.2-rc3-vdso clock-gettime-monotonic: 147 142 clock-getres-monotonic: n/t 34 clock-gettime-monotonic-coarse: 90 96 clock-getres-monotonic-coarse: n/t 36 clock-gettime-monotonic-raw: 431 142 clock-getres-monotonic-raw: n/t 35 clock-gettime-tai: 598 150 clock-getres-tai: n/t 34 clock-gettime-boottime: 592 142 clock-getres-boottime: n/t 34 clock-gettime-realtime: 149 142 clock-getres-realtime: n/t 34 clock-gettime-realtime-coarse: 86 96 clock-getres-realtime-coarse: n/t 36 getcpu: n/t n/t gettimeofday: 133 110 So there are some minor improvements, two minor regressions, some significant improvements (factor 3-4), and some dramatic improvements (where we actually gained VDSO support). Overall a pretty impressive outcome for an "Odd fixes" architecture, especially as it should reduce the future maintenance burden. Cheers, Andre.