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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 6A485C433EF for ; Wed, 8 Sep 2021 18:16:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4333D61041 for ; Wed, 8 Sep 2021 18:16:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240945AbhIHSRU (ORCPT ); Wed, 8 Sep 2021 14:17:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:29304 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233322AbhIHSRU (ORCPT ); Wed, 8 Sep 2021 14:17:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631124971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iytigPz3Y85xtbTRaKagrVG/EYermnbNcHKUwuifyxc=; b=fp4WI1LVNn5bE1pQ6XqRu1pUjVoRtsP1USyGgBKoLWIT+mikLOaQNaoBoUF5fE1HnlDBNq WfM7ROv5x2l6gvbAoXCAN6bGvNLfBfqNoNkuCZiXBTUE7f80M3KTRx0TCBN6I+i/iyy0e/ 6y2u7yW5tVpXkwS1LgL1Bg63dm3lezA= Received: from mail-io1-f72.google.com (mail-io1-f72.google.com [209.85.166.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-204-0OM4AWnCOg2edkdODtnb4Q-1; Wed, 08 Sep 2021 14:16:10 -0400 X-MC-Unique: 0OM4AWnCOg2edkdODtnb4Q-1 Received: by mail-io1-f72.google.com with SMTP id z26-20020a05660200da00b005b86e36a1f4so2445932ioe.15 for ; Wed, 08 Sep 2021 11:16:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=iytigPz3Y85xtbTRaKagrVG/EYermnbNcHKUwuifyxc=; b=LPkcIcMAgefx7m6NNPxadd1Z5hQuqSdTsUa56ZkFLVhBYoGO5oxu6hqjQArfhgrYqR JYBjrA/hsdHilvY/zV2rUg0IU1K9JX1iO1FlkhWudVv5M13bRlINQ8RE01y/Eqvb16YM OD6mgeJVpob3h/xkxSPEzCUPHa3TyX37F5R6XmFC8YAH+3mde/D/c22QrVLO0v/CEBTS LNxXGGF2SWhUC1GWK1Iz+6Vg/l6Zh8PAuwVvo0wDh8WJAdesvP/7gytBWH9Z/rwd0csB 4oAnOSIXFOF/K2wfz7qeThu9bsLuJqvCiR/QHTWkrYzgZXC1d3Z9VlkhQqOEmS+RlKPa evdg== X-Gm-Message-State: AOAM5338PBVrSgFfWV/DynM7CFFX/XIQpqvRndJmaPSYRyZH2V9XnI+f 1ezLGkoqj20BX3nJFRwZFzL0DTej+Xsv9vlrvR/QsqHAw+Qu+N5MuUmpJ4HP4R9nQzIYQkgWhiF yrndQEDEWWH6Ti+iEq2epJjW4tGU= X-Received: by 2002:a05:6602:218d:: with SMTP id b13mr964726iob.143.1631124969382; Wed, 08 Sep 2021 11:16:09 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy4JTdg56EvQA/Z12cYdV0alaWvc7daalGZZzY9T5Xzx/6jrn4jhT3SLlGdvVXcpqp3QgkIpA== X-Received: by 2002:a05:6602:218d:: with SMTP id b13mr964710iob.143.1631124969074; Wed, 08 Sep 2021 11:16:09 -0700 (PDT) Received: from t490s ([2607:fea8:56a3:500::ad7f]) by smtp.gmail.com with ESMTPSA id h1sm1452060iow.12.2021.09.08.11.16.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Sep 2021 11:16:08 -0700 (PDT) Date: Wed, 8 Sep 2021 14:16:06 -0400 From: Peter Xu To: Nicolas Saenz Julienne Cc: linux-rt-users@vger.kernel.org, williams@redhat.com, jkacur@redhat.com Subject: Re: [PATCH 3/3] oslat: Allow for arch specific timer frequency measurements Message-ID: References: <20210908100209.118609-1-nsaenzju@redhat.com> <20210908100209.118609-3-nsaenzju@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210908100209.118609-3-nsaenzju@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Wed, Sep 08, 2021 at 12:02:09PM +0200, Nicolas Saenz Julienne wrote: > Some architectures have special purpose registers to query the system > timer's frequency. Let's use that when available. > > Signed-off-by: Nicolas Saenz Julienne > --- > src/oslat/oslat.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/src/oslat/oslat.c b/src/oslat/oslat.c > index bd155a6..23ca9b6 100644 > --- a/src/oslat/oslat.c > +++ b/src/oslat/oslat.c > @@ -51,6 +51,9 @@ > # define atomic_inc(ptr) __sync_add_and_fetch((ptr), 1) > # if defined(__x86_64__) > # define relax() __asm__ __volatile__("pause" ::: "memory") > + > +#define measure_timer_mhz generic_measure_timer_mhz > + > static inline void frc(uint64_t *pval) > { > uint32_t low, high; > @@ -61,12 +64,18 @@ static inline void frc(uint64_t *pval) > } > # elif defined(__i386__) > # define relax() __asm__ __volatile__("pause" ::: "memory") > + > +#define measure_timer_mhz generic_measure_timer_mhz > + > static inline void frc(uint64_t *pval) > { > __asm__ __volatile__("rdtsc" : "=A" (*pval)); > } > # elif defined(__PPC64__) > # define relax() do { } while (0) > + > +#define measure_timer_mhz generic_measure_timer_mhz > + > static inline void frc(uint64_t *pval) > { > __asm__ __volatile__("mfspr %0, 268\n" : "=r" (*pval)); > @@ -74,6 +83,15 @@ static inline void frc(uint64_t *pval) > # elif defined(__aarch64__) > # define relax() __asm__ __volatile("yield" : : : "memory") > > +static inline unsigned int measure_timer_mhz(void) > +{ > + unsigned int val; > + > + __asm__ __volatile__("mrs %0, cntfrq_el0" : "=r" (val)); > + > + return val / 1e6; > +} > + > static inline void frc(uint64_t *pval) > { > > @@ -257,7 +275,7 @@ static cycles_t __measure_timer_hz(void) > return (cycles_t) ((e - s) / sec); > } > > -static unsigned int measure_timer_mhz(void) > +static unsigned int __attribute__((unused)) generic_measure_timer_mhz(void) This is okay I guess, but does not look nice, as it's marked unused even if it's used.. How about for any arch that supports a faster version to read the freq, do: #define measure_timer_mhz_fast unsigned int measure_timer_mhz_fast(void) { ... } Then at entry of measure_timer_mhz(): #ifdef measure_timer_mhz_fast return measure_timer_mhz_fast(); #endif I'm also wondering the diff between the two methods on arm64 and whether there's a huge difference on the numbers. Thanks, -- Peter Xu