Hi Vincent,
I checked this patch and I can see some performance improvement in my
arm platform also. So in your patch there are 2 changes. First one is
for calculating delay after rate_mult is set, this can be tested with
cpufreq-bench tool. For the second part which requires enabling power
save bias , the cpufreq-bench does not do that. So I tested with one
time setting of powersave_bias parameter and here also there is some
increase in performance. But ideally powersave mode should have more
power saving and some compromise in performance.
//Amit Daniel
On 15 February 2011 04:41, Vincent Guittot <vincent.guittot@xxxxxxxxxx> wrote:
> Hi,
>
> The ondemand delay value is calculated before calling dbs_check_cpu
> which can lead to a delay value of sampling_rate*sampling_down_factor
> but a frequency set to the lowest value. The main result is a slow
> responsiveness during this period. This patch moves the calculation of
> delay after the call of dbs_check_cpu. I have seen this problem when
> testing cpufreq-bench on my Arm platform.
>
> Vincent
>
> On 7 February 2011 17:14, Vincent Guittot <vincent.guittot@xxxxxxxxxx> wrote:
>> calculate ondemand delay after dbs_check_cpu call because it can
>> modify rate_mult value
>>
>> use freq_lo_jiffies value for the sub sample period of powersave_bias mode
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>> ---
>> drivers/cpufreq/cpufreq_ondemand.c | 20 +++++++++++++-------
>> 1 files changed, 13 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq_ondemand.c
>> b/drivers/cpufreq/cpufreq_ondemand.c
>> index 58aa85e..44c2dba 100644
>> --- a/drivers/cpufreq/cpufreq_ondemand.c
>> +++ b/drivers/cpufreq/cpufreq_ondemand.c
>> @@ -641,13 +641,7 @@ static void do_dbs_timer(struct work_struct *work)
>> container_of(work, struct cpu_dbs_info_s, work.work);
>> unsigned int cpu = dbs_info->cpu;
>> int sample_type = dbs_info->sample_type;
>> -
>> - /* We want all CPUs to do sampling nearly on same jiffy */
>> - int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
>> - * dbs_info->rate_mult);
>> -
>> - if (num_online_cpus() > 1)
>> - delay -= jiffies % delay;
>> + int delay;
>>
>> mutex_lock(&dbs_info->timer_mutex);
>>
>> @@ -660,10 +654,22 @@ static void do_dbs_timer(struct work_struct *work)
>> /* Setup timer for SUB_SAMPLE */
>> dbs_info->sample_type = DBS_SUB_SAMPLE;
>> delay = dbs_info->freq_hi_jiffies;
>> + } else {
>> + /* We want all CPUs to do sampling nearly on
>> + * same jiffy
>> + */
>> + delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
>> + * dbs_info->rate_mult);
>> +
>> + if (num_online_cpus() > 1)
>> + delay -= jiffies % delay;
>> +
>> }
>> +
>> } else {
>> __cpufreq_driver_target(dbs_info->cur_policy,
>> dbs_info->freq_lo, CPUFREQ_RELATION_H);
>> + delay = dbs_info->freq_lo_jiffies;
>> }
>> schedule_delayed_work_on(cpu, &dbs_info->work, delay);
>> mutex_unlock(&dbs_info->timer_mutex);
>> --
>> 1.7.1
>>
>
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