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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 B4411C433E0 for ; Wed, 1 Jul 2020 10:46:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F3D020722 for ; Wed, 1 Jul 2020 10:46:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="XD6YuGM9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730052AbgGAKqX (ORCPT ); Wed, 1 Jul 2020 06:46:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729892AbgGAKqW (ORCPT ); Wed, 1 Jul 2020 06:46:22 -0400 Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F4D4C061755 for ; Wed, 1 Jul 2020 03:46:22 -0700 (PDT) Received: by mail-pl1-x643.google.com with SMTP id d10so9760454pls.5 for ; Wed, 01 Jul 2020 03:46:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=FP3q9Hc118M+PIpoZ3gBkp91qt3AttuGKhN6mO4qL+M=; b=XD6YuGM9iKVfQi3Z/Eo2YIh+67TKz1FOxI2pMbOF2fdzKj4x/ZrHc9lj3PEa44zkE9 QI1LjHA9Gl9WjM0zzyeXn3ZqB5HXWdcaPvr7/zgbHq5KhfCvICfkN4MHr8FAkIPlLvzN KkUTwTbPWFRUKcJDisqBoSnbKPWPXwrfGiBYGZKP8E0Ln2fdfJBpIpyPYbMb/iJqfT3N sYjp9VizzuwtgSIAyGNq/9Tg6cUu439NE4bnoMfswrxOvG9M5B28Nnh5+nMRXCicapP1 +wAaRVvT0+tsZZ9iKrFyRSSyvbxcwBYHJyrkVxq8CAA8e8OjTYnNRbudWl8MOkuvIOlH 7gMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=FP3q9Hc118M+PIpoZ3gBkp91qt3AttuGKhN6mO4qL+M=; b=gHGtlV9M6AklvcLzog+/c0tDqqKAbo+Cq/TZedf0taapFoY+ZxuPtC6y4qyIYcoTub 42xGYGbHang/OErpivbHRybOsPWVZoHUSgsymv0qqLjnOuocBNbzXwc/9zMi7o2HYHqs 0e+HympYACauqjRdD6uA/oolTDZ4vBpeB6fswCTUuiHTn6WJNFhl2b6lEze8+YO1nvKD DVgIabxuxBbJgJV14nMHyUM8296JFUM4fRuOhT6IlgzJzqVyVRIAAoAruLzihOYUCEgL S/mRaLoHyLCgS/tsyUhr8cfW5poNwSj211XNHoQN6czVfWZdZnAHzOPvCVEQhJtK89/3 p0iQ== X-Gm-Message-State: AOAM533g7kEY5wJHfUJe6aZjGVGC7EL2feGk10nEhZdQyGjWMqHUeGwG dBizgqbAi96X8qiOFRbeZpvyYg== X-Google-Smtp-Source: ABdhPJwLv9We7Z/3I+LHoShx7LVt8N7F9Lsqh+Ev8MHD230A5RWIRxuOzFuIs+m6GJAlvS45fezEeg== X-Received: by 2002:a17:90b:4d06:: with SMTP id mw6mr29109520pjb.190.1593600381864; Wed, 01 Jul 2020 03:46:21 -0700 (PDT) Received: from localhost ([122.172.81.75]) by smtp.gmail.com with ESMTPSA id r13sm5547968pfr.181.2020.07.01.03.46.20 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Jul 2020 03:46:21 -0700 (PDT) Date: Wed, 1 Jul 2020 16:16:19 +0530 From: Viresh Kumar To: Ionela Voinescu Cc: rjw@rjwysocki.net, catalin.marinas@arm.com, sudeep.holla@arm.com, will@kernel.org, linux@armlinux.org.uk, valentin.schneider@arm.com, mingo@redhat.com, peterz@infradead.org, dietmar.eggemann@arm.com, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/8] cpufreq: move invariance setter calls in cpufreq core Message-ID: <20200701095219.gxrkowtukosnfmwp@vireshk-i7> References: <20200701090751.7543-1-ionela.voinescu@arm.com> <20200701090751.7543-3-ionela.voinescu@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200701090751.7543-3-ionela.voinescu@arm.com> User-Agent: NeoMutt/20180716-391-311a52 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 01-07-20, 10:07, Ionela Voinescu wrote: > From: Valentin Schneider > > To properly scale its per-entity load-tracking signals, the task scheduler > needs to be given a frequency scale factor, i.e. some image of the current > frequency the CPU is running at. Currently, this scale can be computed > either by using counters (APERF/MPERF on x86, AMU on arm64), or by > piggy-backing on the frequency selection done by cpufreq. > > For the latter, drivers have to explicitly set the scale factor > themselves, despite it being purely boiler-plate code: the required > information depends entirely on the kind of frequency switch callback > implemented by the driver, i.e. either of: target_index(), target(), > fast_switch() and setpolicy(). > > The fitness of those callbacks with regard to driving the Frequency > Invariance Engine (FIE) is studied below: > > target_index() > ============== > Documentation states that the chosen frequency "must be determined by > freq_table[index].frequency". It isn't clear if it *has* to be that > frequency, or if it can use that frequency value to do some computation > that ultimately leads to a different frequency selection. All drivers > go for the former, while the vexpress-spc-cpufreq has an atypical > implementation. > > Thefore, the hook works on the asusmption the core can use > freq_table[index].frequency. > > target() > ======= > This has been flagged as deprecated since: > > commit 9c0ebcf78fde ("cpufreq: Implement light weight ->target_index() routine") > > It also doesn't have that many users: > > cpufreq-nforce2.c:371:2: .target = nforce2_target, > cppc_cpufreq.c:416:2: .target = cppc_cpufreq_set_target, > pcc-cpufreq.c:573:2: .target = pcc_cpufreq_target, > > Should we care about drivers using this hook, we may be able to exploit > cpufreq_freq_transition_{being, end}(). Otherwise, if FIE support is > desired in their current state, arch_set_freq_scale() could still be > called directly by the driver, while CPUFREQ_CUSTOM_SET_FREQ_SCALE > could be used to mark support for it. > > fast_switch() > ============= > This callback *has* to return the frequency that was selected. > > setpolicy() > =========== > This callback does not have any designated way of informing what was the > end choice. But there are only two drivers using setpolicy(), and none > of them have current FIE support: > > drivers/cpufreq/longrun.c:281: .setpolicy = longrun_set_policy, > drivers/cpufreq/intel_pstate.c:2215: .setpolicy = intel_pstate_set_policy, > > The intel_pstate is known to use counter-driven frequency invariance. Same for acpi-cpufreq driver as well ? And I think we should do the freq-invariance thing for all the above categories nevertheless. > If FIE support is desired in their current state, arch_set_freq_scale() > could still be called directly by the driver, while > CPUFREQ_CUSTOM_SET_FREQ_SCALE could be used to mark support for it. > > Conclusion > ========== > > Given that the significant majority of current FIE enabled drivers use > callbacks that lend themselves to triggering the setting of the FIE scale > factor in a generic way, move the invariance setter calls to cpufreq core, > while filtering drivers that flag custom support using > CPUFREQ_CUSTOM_SET_FREQ_SCALE. > > Signed-off-by: Valentin Schneider > Signed-off-by: Ionela Voinescu > Cc: Rafael J. Wysocki > Cc: Viresh Kumar > --- > drivers/cpufreq/cpufreq.c | 20 +++++++++++++++++--- > 1 file changed, 17 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 0128de3603df..83b58483a39b 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -2046,9 +2046,16 @@ EXPORT_SYMBOL(cpufreq_unregister_notifier); > unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy, > unsigned int target_freq) > { > + unsigned int freq; > + > target_freq = clamp_val(target_freq, policy->min, policy->max); > + freq = cpufreq_driver->fast_switch(policy, target_freq); > + > + if (freq && !(cpufreq_driver->flags & CPUFREQ_CUSTOM_SET_FREQ_SCALE)) > + arch_set_freq_scale(policy->related_cpus, freq, > + policy->cpuinfo.max_freq); This needs to be a separate function. > > - return cpufreq_driver->fast_switch(policy, target_freq); > + return freq; > } > EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch); > > @@ -2140,7 +2147,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, > unsigned int relation) > { > unsigned int old_target_freq = target_freq; > - int index; > + int index, retval; > > if (cpufreq_disabled()) > return -ENODEV; > @@ -2171,7 +2178,14 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, > > index = cpufreq_frequency_table_target(policy, target_freq, relation); > > - return __target_index(policy, index); > + retval = __target_index(policy, index); > + > + if (!retval && !(cpufreq_driver->flags & CPUFREQ_CUSTOM_SET_FREQ_SCALE)) > + arch_set_freq_scale(policy->related_cpus, > + policy->freq_table[index].frequency, policy->cur gets updated for both target and target_index type drivers. You can use that safely. It gets updated after the postchange notification. > + policy->cpuinfo.max_freq); > + > + return retval; > } > EXPORT_SYMBOL_GPL(__cpufreq_driver_target); -- viresh