From: Lukasz Luba <lukasz.luba@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>,
Rafael Wysocki <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
cristian.marussi@arm.com, sudeep.holla@arm.com,
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 09:21:13 +0100 [thread overview]
Message-ID: <6f794935-a5d2-0f4d-70d7-de4705ba9511@arm.com> (raw)
In-Reply-To: <31999d801bfb4d8063dc1ceec1234b6b80b4ae68.1600238586.git.viresh.kumar@linaro.org>
On 9/16/20 7:45 AM, Viresh Kumar wrote:
> In order to prepare for lock-less stats update, add support to defer any
> updates to it until cpufreq_stats_record_transition() is called.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> drivers/cpufreq/cpufreq_stats.c | 75 ++++++++++++++++++++++++---------
> 1 file changed, 56 insertions(+), 19 deletions(-)
>
[snip]
> @@ -228,10 +264,11 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
> struct cpufreq_stats *stats = policy->stats;
> int old_index, new_index;
>
> - if (!stats) {
> - pr_debug("%s: No stats found\n", __func__);
> + if (!stats)
> return;
> - }
> +
> + if (READ_ONCE(stats->reset_pending))
> + cpufreq_stats_reset_table(stats);
>
This is in the hot path code, called from the scheduler. I wonder if we
avoid it or make that branch 'unlikely'?
if (unlikely(READ_ONCE(stats->reset_pending)))
Probably the CPU (when it has good prefetcher) would realize about it,
but maybe we can help a bit here.
next prev parent reply other threads:[~2020-09-25 8:21 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
2020-09-25 11:26 ` Viresh Kumar
2020-09-25 8:21 ` Lukasz Luba [this message]
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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