linux-kernel - Re: [PATCH] cpufreq: stats: clear statistics

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Message-ID: <20161104021206.GJ10786@vireshk-i7>
Date:   Fri, 4 Nov 2016 07:42:06 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Markus Mayer <code@...yer.net>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Power Management List <linux-pm@...r.kernel.org>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Markus Mayer <mmayer@...adcom.com>
Subject: Re: [PATCH] cpufreq: stats: clear statistics

On 04-11-16, 01:28, Rafael J. Wysocki wrote:
> On Thu, Nov 3, 2016 at 9:46 PM, Markus Mayer <code@...yer.net> wrote:
> > From: Markus Mayer <mmayer@...adcom.com>
> >
> > Allow cpufreq statistics to be cleared by writing anything to
> > /sys/.../cpufreq/stats/reset. Reading this new sysfs entry returns
> > nothing.
> >
> > Resetting the statistics can be useful in a test environment (test
> > governor, retrieve stats, reset stats, test other governor, etc.). This
> > feature is not meant for production use.
> >
> > Signed-off-by: Markus Mayer <mmayer@...adcom.com>
> > ---
> >  drivers/cpufreq/Kconfig         | 10 ++++++++++
> >  drivers/cpufreq/cpufreq_stats.c | 32 ++++++++++++++++++++++++++++++++
> >  2 files changed, 42 insertions(+)
> >
> > diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> > index d8b164a..97a458e 100644
> > --- a/drivers/cpufreq/Kconfig
> > +++ b/drivers/cpufreq/Kconfig
> > @@ -45,6 +45,16 @@ config CPU_FREQ_STAT_DETAILS
> >
> >           If in doubt, say N.
> >
> > +config CPU_FREQ_STAT_RESET
> > +       bool "Allow reset of CPU frequency transition statistics"
> > +       depends on CPU_FREQ_STAT
> > +       help
> > +         If enabled, writing to /sys/[...]/cpufreq/stats/reset will reset the
> > +         current CPUfreq statistics. This is primarily meant for testing. It
> > +         should not be enabled on a production system.
> > +
> > +         If in doubt, say N.
> > +
> >  choice
> >         prompt "Default CPUFreq governor"
> >         default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
> > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
> > index 06d3abd..e4e1e3e 100644
> > --- a/drivers/cpufreq/cpufreq_stats.c
> > +++ b/drivers/cpufreq/cpufreq_stats.c
> > @@ -111,6 +111,35 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
> >  cpufreq_freq_attr_ro(trans_table);
> >  #endif
> >
> > +#ifdef CONFIG_CPU_FREQ_STAT_RESET
> > +static void cpufreq_stats_clear_table(struct cpufreq_policy *policy)
> > +{
> > +       struct cpufreq_stats *stats = policy->stats;
> > +       unsigned int count = stats->max_state;
> > +
> > +       memset(stats->time_in_state, 0, count * sizeof(u64));
> > +#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
> > +       memset(stats->trans_table, 0, count * count * sizeof(int));
> > +#endif
> > +       stats->last_time = get_jiffies_64();
> > +       stats->total_trans = 0;
> > +}
> > +
> > +static ssize_t show_reset(struct cpufreq_policy *policy, char *buf)
> > +{
> > +       buf[0] = '\0';
> > +       return 0;
> > +}
> > +
> > +static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
> > +                          size_t count)
> > +{
> > +       cpufreq_stats_clear_table(policy);
> > +       return count;
> > +}
> > +cpufreq_freq_attr_rw(reset);
> > +#endif
> > +
> >  cpufreq_freq_attr_ro(total_trans);
> >  cpufreq_freq_attr_ro(time_in_state);
> >
> > @@ -120,6 +149,9 @@ static struct attribute *default_attrs[] = {
> >  #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
> >         &trans_table.attr,
> >  #endif
> > +#ifdef CONFIG_CPU_FREQ_STAT_RESET
> > +       &reset.attr,
> > +#endif
> >         NULL
> >  };
> >  static struct attribute_group stats_attr_group = {
> > --
> 
> What would be wrong with adding this unconditionally?

Absolutely and there is no need to have read permissions for the file. Just make
it write only.

-- 
viresh