Hi Amit,

Thanks for this input about performance improvement.

For the powersave_bias mode, it's normal that you have some performances improvement because we run freq_lo_jiffies in low freq and freq_high_jiffies in high freq with (freq_lo_jiffies + freq_high_jiffies) = sample_rate whereas the duration was sample_rate in low freq before. you can also note that powersave_bias feature doesn't use the sampling_down factor

Vincent

On 21 February 2011 10:38, Amit Kachhap amit.kachhap@linaro.org wrote:

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@linaro.org 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@linaro.org 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@linaro.org

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

---

linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev