Re: [patch] CFS scheduler, -v8

Ting Yang
2007-05-02T23:42:00Z

Srivatsa Vaddagiri wrote:
> I briefly went thr' the paper and my impression is it expect each task
> to specify the length of each new request it initiates. Is that correct?
>
No, the timeslice l_i here serves as a granularity control w.r.t
responsiveness (or latency depends on how you interpret it). As wli said
it can be express as a function of the priority, as we do for weight
now. It is not related with the length of each new request. A request
may be 1 seconds long, but the scheduler may still process it using 10ms
timeslice. Smaller timeslice leads to more accuracy, i.e. closer to
ideal case.
However, the maximum of timeslice l_i used by all active tasks
determines the total responsiveness of the system, which I will explain
in detail later.
> There is also p->wait_runtime which is taken into account when
> calculating p->fair_key. So if p3 had waiting in runqueue for long
> before, it can get to run quicker than 10ms later.
Consider if p3 is a newly started task or waked up task and carries no
p->wait_runtime.

Ting