From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Rafael Wysocki <rjw@rjwysocki.net>,
Linux PM <linux-pm@vger.kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Lukasz Luba <lukasz.luba@arm.com>,
cristian.marussi@arm.com, Sudeep Holla <sudeep.holla@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2 1/4] cpufreq: stats: Defer stats update to cpufreq_stats_record_transition()
Date: Fri, 25 Sep 2020 13:09:30 +0200 [thread overview]
Message-ID: <CAJZ5v0guU0GDs06W98boFpdCopHTiF_ojwTPrZFNP0Bk3DiQXQ@mail.gmail.com> (raw)
In-Reply-To: <20200925105830.xsmiwkjohlqb5joj@vireshk-i7>
On Fri, Sep 25, 2020 at 12:58 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 25-09-20, 12:04, Rafael J. Wysocki wrote:
> > I'm actually wondering if reset_time is necessary at all.
> >
> > If cpufreq_stats_record_transition() is the only updater of the stats,
> > which will be the case after applying this series IIUC, it may as well
> > simply set the new starting point and discard all of the data
> > collected so far if reset_pending is set.
> >
> > IOW, the time when the reset has been requested isn't particularly
> > relevant IMV (and it is not exact anyway), because the user is
> > basically asking for discarding "history" and that may very well be
> > interpreted to include the current sample.
>
> There are times when this would be visible to userspace and won't look nice.
>
> Like, set governor to performance, reset the stats and after 10 seconds, read
> the stats again, everything will be 0.
Unless I'm missing something, the real reset happens when
cpufreq_stats_record_transition() runs next time, so the old stats
will still be visible at that point, won't they?
> Because cpufreq_stats_record_transition()
> doesn't get called at all here, we would never clear them until the time
> governor is changed and so we need to keep a track of reset-time.
Or trigger a forced update.
next prev parent reply other threads:[~2020-09-25 11:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 6:45 [PATCH V2 0/4] cpufreq: Record stats with fast-switching Viresh Kumar
2020-09-16 6:45 ` [PATCH V2 1/4] cpufreq: stats: Defer stats update to cpufreq_stats_record_transition() Viresh Kumar
2020-09-23 13:48 ` Rafael J. Wysocki
2020-09-24 9:25 ` Lukasz Luba
2020-09-24 10:24 ` Rafael J. Wysocki
2020-09-24 11:00 ` Lukasz Luba
2020-09-24 11:07 ` Rafael J. Wysocki
2020-09-24 12:39 ` Viresh Kumar
2020-09-24 16:10 ` Lukasz Luba
2020-09-25 6:09 ` Viresh Kumar
2020-09-25 8:10 ` Lukasz Luba
2020-09-24 13:15 ` Viresh Kumar
2020-09-25 10:04 ` Rafael J. Wysocki
2020-09-25 10:58 ` Viresh Kumar
2020-09-25 11:09 ` Rafael J. Wysocki [this message]
2020-09-25 11:26 ` Viresh Kumar
2020-09-25 8:21 ` Lukasz Luba
2020-09-25 10:46 ` Viresh Kumar
2020-09-16 6:45 ` [PATCH V2 2/4] cpufreq: stats: Remove locking Viresh Kumar
2020-09-16 6:45 ` [PATCH V2 3/4] cpufreq: stats: Enable stats for fast-switch as well Viresh Kumar
2020-09-23 15:14 ` Rafael J. Wysocki
2020-09-23 15:17 ` Rafael J. Wysocki
2020-09-16 6:45 ` [PATCH V2 4/4] cpufreq: Move traces and update to policy->cur to cpufreq core Viresh Kumar
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