Re: [PATCH 0/1] fs/resctrl: Show domain CPU list in schema output

Aaron Tomlin
2025-10-31T21:25:50Z

On Fri, Oct 31, 2025 at 07:03:15PM +0000, Luck, Tony wrote:
> 1) You'd also need to change the "write" path for the schemata file
> (treating the CPU list as read-only).
>
> 2) This would break user ABI, so is not going to happen.

Hi Tony,

Thank you for following up.

If I understand correctly, parse_cbm() and parse_bw() would return -EINVAL
if the user incorrectly included the CPU list, no?

I suspect the issue is if one can read something from a file, one should be
able to write the same thing back and have it either succeed or process
only the valid parts. I agree maintaining ABI compatibility while allowing
the new verbose output on the read path is not ideal.

> Users can see the association between the domain numbers and
> CPUs in sysfs.
>
> $ cat /sys/devices/system/cpu/cpu0/cache/index3/id
> 0
> $ cat /sys/devices/system/cpu/cpu0/cache/index3/shared_cpu_list
> 0-27
>
> Maybe not as convenient as a direct read-out in the schemata file.
> But the information is easily accessible.

No, using the above to establish the association is absolutely fine.

Kind regards,

--
Aaron Tomlin