Re: [PATCH V2 3/3] workqueue: Schedule work on non-idle cpu insteadof current one

[Viresh Kumar]

On 1 October 2012 06:02, Tejun Heo <tj@xxxxxxxxxx> wrote:
> It isn't about the CPU being actually idle?

No. Being idle only from scheduler's perspective. :)

> Also, if it's only about timers, shouldn't it be enough to implement
> it for timer and delayed_work?

What if we need a timer, which must re-arm itself + schedule a work?
delayed_work will not be sufficient in that case, and we would need
to use normal work.

If i am not wrong, there can be other future users of this routine too.
@Vincent: Can you please comment on this?

> It would be great if you explain what you're trying to achieve how.  I
> can't tell what you're aiming for and why that would be beneficial
> from these submissions.

Following slides are implemented by Vincent and presented during LPC.
Please have a look at them, they explain the problem statement well:

http://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/08/lpc2012-sched-timer-workqueue.pdf

Specifically slides: 12 & 19.

There aren't too many users with this behavior, but even a single user
will be sufficient not to let the cpu get idle at all. And that will result in
less power saving.

--
viresh
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