Re: [RFC PATCH v2 0/2] sched: Nominate a power-efficient ILB

Suresh Siddha
2009-04-22T01:06:54Z

On Mon, 2009-04-13 at 21:55 -0700, Gautham R Shenoy wrote:
> Now, the other power-savings settings such as the sched_mc/smt_power_savings
> and the power-aware IRQ balancer try to balance tasks/IRQs by taking
> the system topology into consideration, with the intention of keeping
> as many "power-domains" (cores/packages) in the low-power state.
>
> The current idle-load-balancer nomination does not necessarily align towards
> this policy. For eg, we could be having tasks and interrupts largely running
> on the first package with the intention of keeping the second package idle.
> Hence, CPU 0 may be busy. The first_cpu in the nohz.cpu_mask happens to be CPU1,
> which in-turn becomes nominated as the idle-load balancer. CPU1 being from
> the 2nd package, would in turn prevent the 2nd package from going into a
> deeper sleep state.
>
> Instead the role of the idle-load balancer could have been assumed by an
> idle CPU from the first package, thereby helping the second package go
> completely idle.

Can we also do this by default? i.e., even when no power-savings policy
is selected.

I don't see anything wrong by enabling this logic for all the cases.

thanks,
suresh