On Sat, Sep 07, 2013 at 06:35:08PM +0200, Frederic Weisbecker wrote: > The time spent by a CPU under a given frequency is stored in jiffies unit > in the cpu var cpufreq_stats_table->time_in_state[i], i being the index of > the frequency. > > This is what is displayed in the following file on the right column: > > cat /sys/devices/system/cpu/cpuX/cpufreq/stats/time_in_state > 2301000 19835820 > 2300000 3172 > [...] > > Now cpufreq converts this jiffies unit delta to clock_t before returning it > to the user as in the above file. And that conversion is achieved using the > API > cputime64_to_clock_t(). > > Although it accidentally works on traditional tick based cputime accounting, > where > cputime_t maps directly to jiffies, it doesn't work with other types of > cputime > accounting such as CONFIG_VIRT_CPU_ACCOUNTING_* where cputime_t can map to > nsecs > or any granularity preffered by the architecture. > > For example we get a buggy zero delta on full dyntick configurations: > > cat /sys/devices/system/cpu/cpuX/cpufreq/stats/time_in_state > 2301000 0 > 2300000 0 > [...] > > Fix this with using the proper jiffies_64_t to clock_t conversion. > > Reported-by: Carsten Emde <[email protected]> > Tested-by: Carsten Emde <[email protected]> > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Carsten Emde <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Clark Williams <[email protected]> > Cc: Sebastian Andrzej Siewior <[email protected]> > Cc: Paul E. McKenney <[email protected]>
Good catch! Acked-by: Paul E. McKenney <[email protected]> > --- > drivers/cpufreq/cpufreq_stats.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c > index d37568c..10e6138 100644 > --- a/drivers/cpufreq/cpufreq_stats.c > +++ b/drivers/cpufreq/cpufreq_stats.c > @@ -81,7 +81,7 @@ static ssize_t show_time_in_state(struct cpufreq_policy > *policy, char *buf) > for (i = 0; i < stat->state_num; i++) { > len += sprintf(buf + len, "%u %llu\n", stat->freq_table[i], > (unsigned long long) > - cputime64_to_clock_t(stat->time_in_state[i])); > + jiffies_64_to_clock_t(stat->time_in_state[i])); > } > return len; > } > -- > 1.7.5.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
