Re: 32bit resctrl? (was Re: [PATCH v2] fs/resctrl: fix domid loss precision issue)

[Peter Newman]

Hi Rex,

On Thu, Mar 14, 2024 at 8:25 AM Reinette Chatre
<reinette.chatre@xxxxxxxxx> wrote:
>
> +x86 maintainers, Tony, Babu, Peter
>
> Hi Everybody,
>
> On 3/12/2024 12:53 AM, Rex Nie wrote:
> > Below statement from mkdir_mondata_subdir function will loss precision,
> > because it assigns int to 14 bits bitfield.
> >       priv.u.domid = d->id;
> >
> > On some platforms(e.g.,x86), the max cache_id is the amount of L3 caches,
> > so it is not in the range of 0x3fff. But some platforms use higher
> > cache_id, e.g., arm uses cache_id as locator for cache MSC. This will
> > cause below issue if cache_id > 0x3fff likes:
> > /sys/fs/resctrl/mon_groups/p1/mon_data/mon_L3_1048564 # cat llc_occupancy

This domain ID seems unreadable in decimal and I'm wondering whether
it's the best value to use to identify the domain. Does this system
have over 1 million L3 domains?

Thanks!
-Peter