Re: [RFD] resctrl: reassigning a running container's CTRL_MON group

[Peter Newman]

Hi James,

On Tue, Oct 25, 2022 at 5:56 PM James Morse <james.morse@xxxxxxx> wrote:
> This would work when systems are built to look like RDT, but MPAM has other control types
> where this would have interesting behaviours.
>
> 'CPOR' is equivalent to CBM as they are both a bitmap of portions. MPAM also has 'CMAX'
> where a fraction of the cache is specified. If you create two control groups with
> different PARTIDs but the same configuration, their two 50%s of the cache could become
> 100%. CPOR can be used like this, CMAX can't.

I thought we only allocated caches with CBMs and memory bandwidth with
percentages.
I don't see how CMAX could be used when implementing resctrl's CAT
resources. Percentage
configurations are only used for MBA in resctrl today.

> Even when the controls behave in the same way, a different PARTID with the same control
> values could be regulated differently, resulting in weirdness.

Can you provide further examples?

-Peter