Re: [RFC 0/2] Optimize the idle CPU search

[Subhra Mazumdar]

On 7/9/19 11:08 AM, Parth Shah wrote:
> On 7/9/19 5:38 AM, Subhra Mazumdar wrote:
> > On 7/8/19 10:24 AM, Parth Shah wrote:
> > > When searching for an idle_sibling, scheduler first iterates to search for
> > > an idle core and then for an idle CPU. By maintaining the idle CPU mask
> > > while iterating through idle cores, we can mark non-idle CPUs for which
> > > idle CPU search would not have to iterate through again. This is especially
> > > true in a moderately load system
> > >
> > > Optimize idle CPUs search by marking already found non idle CPUs during
> > > idle core search. This reduces iteration count when searching for idle
> > > CPUs, resulting in lower iteration count.
> > I believe this can co-exist with latency-nice? We can derive the 'nr' in
> > select_idle_cpu from latency-nice and use the new mask to iterate.
> I agree, can be done with latency-nice.
>
> Maybe something like below?
> smt = nr_cpus / nr_cores
> nr = smt + (p->latency_nice * (total_cpus-smt) / max_latency_nice)
>
> This limits lower bounds to 1 core and goes through all the cores if
> latency_nice is maximum for a task.
Yes I had similar in mind.