Re: [patch v5 10/15] sched: packing transitory tasks in wake/exec power balancing

Alex Shi
2013-02-20T08:11:24Z

On 02/20/2013 03:40 PM, Mike Galbraith wrote:
> On Wed, 2013-02-20 at 13:55 +0800, Alex Shi wrote:
>
>> Joonsoo Kim suggests not packing exec task, since the old task utils is
>> possibly unuseable.
>
> (I'm stumbling around in rtmutex PI land, all dazed and confused, so
> forgive me if my peripheral following of this thread is off target;)
>
> Hm, possibly. Future behavior is always undefined, trying to predict
> always a gamble... so it looks to me like not packing on exec places a
> bet against the user, who chose to wager that powersaving will happen
> and it won't cost him too much, if you don't always try to pack despite
> any risks. The user placed a bet on powersaving, not burst performance.
>
> Same for the fork, if you spread to accommodate a potential burst, you
> bin the power wager, so maybe it's not in his best interest.. fork/exec
> is common, if it's happening frequently, you'll bin the potential power
> win frequently, reducing effectiveness, and silently trading power for
> performance when the user asked to trade performance for a lower
> electric bill.
>
> Dunno, just a thought, but I'd say for powersaving policy, you have to
> go just for broke and hope it works out. You can't know it won't, but
> you'll toss potential winnings every time you don't roll the dice.

Sounds reasonable too.

I have no idea of the of the decision now.
And guess many guys dislike to use a knob to let user do the choice.

What's your opinions, Peter?
>
> -Mike
>

--
Thanks Alex