Re: [PATCH] sched/arm64: store cpu topology before notify_cpu_starting

[chengjian (D)]

On 2020/4/10 1:54, Joel Fernandes wrote:
> On Wed, Apr 1, 2020 at 7:27 AM Cheng Jian <cj.chengjian@xxxxxxxxxx> wrote:
> > when SCHED_CORE enabled, sched_cpu_starting() uses thread_sibling as
> > SMT_MASK to initialize rq->core, but only after store_cpu_topology(),
> > the thread_sibling is ready for use.
> >
> >          notify_cpu_starting()
> >              -> sched_cpu_starting()     # use thread_sibling
> >
> >          store_cpu_topology(cpu)
> >              -> update_siblings_masks    # set thread_sibling
> >
> > Fix this by doing notify_cpu_starting later, just like x86 do.
> >
> > Signed-off-by: Cheng Jian <cj.chengjian@xxxxxxxxxx>
> Just a high-level question, why does core-scheduling matter on ARM64?
> Is it for HPC workloads?
>
> Thanks,
>
>   - Joel

Hi, Joel

I am analyzing the mainline scheduling patches and find this problem.


ARM has some platforms that support SMT, and provides some emulate

can be used.



Thanks.

--Cheng Jian