Re: [PATCH v2 1/4] sched/isolation: API to get housekeeping online CPUs

[peterz]

On Wed, Sep 23, 2020 at 02:11:23PM -0400, Nitesh Narayan Lal wrote:
> Introduce a new API hk_num_online_cpus(), that can be used to
> retrieve the number of online housekeeping CPUs that are meant to handle
> managed IRQ jobs.
> 
> This API is introduced for the drivers that were previously relying only
> on num_online_cpus() to determine the number of MSIX vectors to create.
> In an RT environment with large isolated but fewer housekeeping CPUs this
> was leading to a situation where an attempt to move all of the vectors
> corresponding to isolated CPUs to housekeeping CPUs were failing due to
> per CPU vector limit.
> 
> Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx>
> ---
>  include/linux/sched/isolation.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
> index cc9f393e2a70..2e96b626e02e 100644
> --- a/include/linux/sched/isolation.h
> +++ b/include/linux/sched/isolation.h
> @@ -57,4 +57,17 @@ static inline bool housekeeping_cpu(int cpu, enum hk_flags flags)
>  	return true;
>  }
>  
> +static inline unsigned int hk_num_online_cpus(void)

This breaks with the established naming of that header.