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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 47748C33CB1 for ; Fri, 17 Jan 2020 09:00:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1BEA52082F for ; Fri, 17 Jan 2020 09:00:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726596AbgAQJAA (ORCPT ); Fri, 17 Jan 2020 04:00:00 -0500 Received: from gate.crashing.org ([63.228.1.57]:51278 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726908AbgAQJAA (ORCPT ); Fri, 17 Jan 2020 04:00:00 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 00H8ws29002697; Fri, 17 Jan 2020 02:58:54 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 00H8wpV1002692; Fri, 17 Jan 2020 02:58:51 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 17 Jan 2020 02:58:51 -0600 From: Segher Boessenkool To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , nathanl@linux.ibm.com, arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org Subject: Re: [RFC PATCH v4 00/11] powerpc: switch VDSO to C implementation. Message-ID: <20200117085851.GS3191@gate.crashing.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Hi! On Thu, Jan 16, 2020 at 05:58:24PM +0000, Christophe Leroy wrote: > On a powerpc8xx, with current powerpc/32 ASM VDSO: > > gettimeofday: vdso: 907 nsec/call > clock-getres-realtime: vdso: 484 nsec/call > clock-gettime-realtime: vdso: 899 nsec/call > > The first patch adds VDSO generic C support without any changes to common code. > Performance is as follows: > > gettimeofday: vdso: 1211 nsec/call > clock-getres-realtime: vdso: 722 nsec/call > clock-gettime-realtime: vdso: 1216 nsec/call > > Then a few changes in the common code have allowed performance improvement. At > the end of the series we have: > > gettimeofday: vdso: 974 nsec/call > clock-getres-realtime: vdso: 545 nsec/call > clock-gettime-realtime: vdso: 941 nsec/call > > The final result is rather close to pure ASM VDSO: > * 7% more on gettimeofday (9 cycles) > * 5% more on clock-gettime-realtime (6 cycles) > * 12% more on clock-getres-realtime (8 cycles) Nice! Much better. It should be tested on more representative hardware, too, but this looks promising alright :-) Segher