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SubjectRe: [RFC PATCH v3 0/5] Tunable sched_mc_power_savings=n
* Peter Zijlstra <> [2008-11-10 19:50:16]:

> a quick response, I'll read them more carefully tomorrow:

Hi Peter,

Thanks for the quick review.

> - why are the preferred cpu things pointers? afaict using just the cpu
> number is both smaller and clearer to the reader.

I would need each cpu within a partitioned sched domain to point to
the _same_ preferred wakeup cpu. The preferred CPU will be updated in
one place in find_busiest_group() and used by wake_idle.

If I have a per cpu value, then updating it for each cpu in the
partitioned sched domain will be slow.

The actual number of preferred_wakeup_cpu will be equal to the number
of partitions. If there are no partitions in the sched domains, then
then all per-cpu pointers will point to the same variable.

> - in patch 5/5 you do:
> + spin_unlock(&this_rq->lock);
> + double_rq_lock(this_rq, busiest);
> we call that double_lock_balance()

Will fix this. Did not look for such a routine :)

> - comments go like:
> /*
> * this is a multi-
> * line comment
> */

Will fix this too.


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