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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 25B29C3A59E for ; Wed, 21 Aug 2019 21:17:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01E6922CF7 for ; Wed, 21 Aug 2019 21:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729942AbfHUVRj (ORCPT ); Wed, 21 Aug 2019 17:17:39 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:57695 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727136AbfHUVRj (ORCPT ); Wed, 21 Aug 2019 17:17:39 -0400 Received: from p5de0b6c5.dip0.t-ipconnect.de ([93.224.182.197] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1i0Xz6-0005hh-PC; Wed, 21 Aug 2019 23:17:36 +0200 Date: Wed, 21 Aug 2019 23:17:35 +0200 (CEST) From: Thomas Gleixner To: Vitaly Kuznetsov cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Sasha Levin , Daniel Lezcano , Michael Kelley , Tianyu Lan , Peter Zijlstra Subject: Re: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit In-Reply-To: <20190821095650.1841-1-vkuznets@redhat.com> Message-ID: References: <20190821095650.1841-1-vkuznets@redhat.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Aug 2019, Vitaly Kuznetsov wrote: > There is no particular reason to not enable TSC page clocksource > on 32-bit. mul_u64_u64_shr() is available and despite the increased > computational complexity (compared to 64bit) TSC page is still a huge > win compared to MSR-based clocksource. > > In-kernel reads: > MSR based clocksource: 3361 cycles > TSC page clocksource: 49 cycles > > Reads from userspace (unilizing vDSO in case of TSC page): > MSR based clocksource: 5664 cycles > TSC page clocksource: 131 cycles > > Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE s/allows us/allows/ > as it is now not any different from CONFIG_HYPERV_TIMER. > > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/include/asm/vdso/gettimeofday.h | 6 +++--- > drivers/clocksource/hyperv_timer.c | 11 ----------- > drivers/hv/Kconfig | 3 --- > include/clocksource/hyperv_timer.h | 6 ++---- > 4 files changed, 5 insertions(+), 21 deletions(-) Really nice cleanup as a side effect of adding functionality. Thanks, tglx