Re: [PATCH v3 06/19] x86/resctrl: Allow the allocator to check if a CLOSID can allocate clean RMID

[Reinette Chatre]

Hi James,

On 3/20/2023 10:26 AM, James Morse wrote:

...

> +/**
> + * resctrl_closid_is_dirty - Determine if all RMID associated with this CLOSID
> + *                           are available.
> + * @closid: The CLOSID that is being queried.
> + *
> + * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
> + * may not be able to allocate clean RMID. To avoid this the allocator will
> + * only return clean CLOSID. This is enough for now as it allows MPAM systems
> + * to use resctrl. This suffers from the problem that there may be no CLOSID
> + * where all the RMID are clean, causing the CLOSID allocation to fail.
> + * This can be improved (once MPAM support is upstream) to return the cleanest
> + * CLOSID where PMG=0 is clean. This would allow the CLOSID allocation to

Why does PMG=0 have to be the clean ID? 

I am wondering about the use cases here. When a new CLOSID needs to be allocated,
would it not be useful to instead have a utility that returns the "cleanest" CLOSID?
Instead of picking an available CLOSID and then always have to check if it is
"dirty or not", why not have a utility that picks the CLOSID with the most
available PMGs?

Reinette