linux-kernel - Re: [patch] CFS scheduler, -v14

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Date:	Fri, 01 Jun 2007 15:16:55 +0800
From:	Li Yu <raise.sail@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [patch] CFS scheduler, -v14

Ingo Molnar wrote:
> * Li Yu <raise.sail@...il.com> wrote:
>
>   
>> static void distribute_fair_add(struct rq *rq, s64 delta)
>> {
>>    struct task_struct *curr = rq->curr;
>>    s64 delta_fair = 0;
>>
>>    if (!(sysctl_sched_load_smoothing & 32))
>>        return;
>>
>>    if (rq->nr_running) {
>>        delta_fair = div64_s(delta, rq->nr_running);
>>        /*
>>         * The currently running task's next wait_runtime value does
>>         * not depend on the fair_clock, so fix it up explicitly:
>>         */
>>        add_wait_runtime(rq, curr, -delta_fair);
>>        rq->fair_clock -= delta_fair;
>>    }
>> }
>>
>> See this line:
>>
>>        delta_fair = div64_s(delta, rq->nr_running);
>>
>> Ingo, should we be replace "rq->nr_running" with "rq->raw_load_weight" 
>> here?
>>     
>
> that would break the code. The handling of sleep periods is basically 
> heuristics and using nr_running here appears to be 'good enough' in 
> practice.
>
>   
Thanks,  I am wrong at seeing the delta variable is represented by 
virtual time unit. if the code does as I said, the delta_fair may be too 
small to meanless.

Also, I have want to know what's real meaning of     

    add_wait_runtime(rq, curr, delta_mine - delta_exec);

in update_curr(), IMHO, it should be

    add_wait_runtime(rq, curr, delta_mine - delta_fair);

Is this just another heuristics? or my opinion is wrong again? :-)

Good luck.

- Li Yu





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