Re: [patch v5 06/15] sched: log the cpu utilization at rq

Alex Shi
2013-02-20T14:34:04Z

On 02/20/2013 05:30 PM, Peter Zijlstra wrote:
> On Mon, 2013-02-18 at 13:07 +0800, Alex Shi wrote:
>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index fcdb21f..b9a34ab 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -1495,8 +1495,12 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
>>
>> static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
>> {
>> + u32 period;
>> __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
>> __update_tg_runnable_avg(&rq->avg, &rq->cfs);
>> +
>> + period = rq->avg.runnable_avg_period ? rq->avg.runnable_avg_period : 1;
>> + rq->util = rq->avg.runnable_avg_sum * 100 / period;
>> }
>>
>> /* Add the load generated by se into cfs_rq's child load-average */
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 7a19792..ac1e107 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -350,6 +350,9 @@ extern struct root_domain def_root_domain;
>>
>> #endif /* CONFIG_SMP */
>>
>> +/* the percentage full cpu utilization */
>> +#define FULL_UTIL 100
>
> There's generally a better value than 100 when using computers.. seeing
> how 100 is 64+32+4.

I didn't find a good example for this. and no idea of your suggestion,
would you like to explain a bit more?

>
>> +
>> /*
>> * This is the main, per-CPU runqueue data structure.
>> *
>> @@ -481,6 +484,7 @@ struct rq {
>> #endif
>>
>> struct sched_avg avg;
>> + unsigned int util;
>> };
>>
>> static inline int cpu_of(struct rq *rq)
>
> You don't actually compute the rq utilization, you only compute the
> utilization as per the fair class, so if there's significant RT activity
> it'll think the cpu is under-utilized, whihc I think will result in the
> wrong thing.

yes. A bit complicit to resolve this. Any suggestions on this, guys?
>

--
Thanks
Alex