Re: [PATCH v4 5/7] fs/resctrl: Continue counter allocation after failure

Reinette Chatre
2026-04-15T14:27:59Z

Hi Ben,

On 4/14/26 7:42 AM, Ben Horgan wrote:
> On 3/27/26 16:21, Reinette Chatre wrote:

>> Consider a changelog like below that just focuses on problem being solved
>> (but please correct me if you find I am missing the point):
>>
>> In mbm_event mode, with mbm_assign_on_mkdir set to 1, when a user
>> creates a new CTRL_MON or MON group resctrl attempts to allocate
>> counters for each of the supported MBM events on each resctrl
>> domain. As counters are limited, such allocation may fail and
>> when it does counter allocations for the remaining domains are
>> skipped even if the domains have available counters.
>>
>> Since a counter allocation failure may result in counter allocation
>> skipped on other domains the user needs to view the resource group's
>
> skipped -> being skipped
>
>> mbm_L3_assignments files to get an accurate view of counter assignment
>> in a new resource group and then manually create counters in the skipped
>> domains with available counters.
>>
>> Writes to mbm_L3_assignments using the wildcard format, <event>:*=e,
>> also skip counter allocation in other domains after a counter allocation
>> failure.
>>
>> When handling a request to create counters in all domains it is unnecessary
>> for a counter allocation in one domain to prevent counter allocation in
>> other domains. Always attempt to allocate all the counters requested.
>
> I can use this but how about if I add,
>
> Skipping counter allocation in subsequent domains after failure makes predicting which
> counters will be allocated harder for the user as they need to know the ordering of the
> domains as well as the expected failures.

I do not see why the user needs to make any predictions with the current implementation.
mbm_L3_assignments will always contain accurate information regarding counter assignment, no?

>
> before the final sentence to make it clear that this change is an improvement not just
> a change in policy.

Reinette