Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH] cpufreq: Fix wrong time unit conversion | Date | Sat, 7 Sep 2013 18:35:08 +0200 |
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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 <C.Emde@osadl.org> Tested-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Carsten Emde <C.Emde@osadl.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Clark Williams <williams@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- 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
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