On Thu, May 22, 2025 at 02:51:36PM -0500, Babu Moger wrote:
>
> +/*
> + * resctrl_io_alloc_closid_get - io_alloc feature uses max CLOSID to route
> + * the IO traffic. Get the max CLOSID and verify if the CLOSID is available.
> + *
> + * The total number of CLOSIDs is determined in closid_init(), based on the
> + * minimum supported across all resources. If CDP (Code Data Prioritization)
> + * is enabled, the number of CLOSIDs is halved. The final value is returned
> + * by closids_supported(). Make sure this value aligns with the maximum
> + * CLOSID supported by the respective resource.
> + */
> +static int resctrl_io_alloc_closid_get(struct rdt_resource *r)
> +{
> + int num_closids = closids_supported();
> +
> + if (resctrl_arch_get_cdp_enabled(r->rid))
> + num_closids *= 2;
> +
> + if (num_closids != resctrl_arch_get_num_closid(r))
> + return -ENOSPC;
> +
> + return closids_supported() - 1;
> +}
Is using closids_supported() the right thing here? That's
the minimum value across all resources. So suppose you had
16 CLOS for the L3 resource, but only 8 CLOS in one of L2/MB/SMBA.
I'd assume the your h/w doesn't care that Linux chose to
ignore half of the available L3 CLOSIDs, and is still going
to use CLOSID==15 for SDCIA.
I think you'll take the -ENOSPC error return. But do you
really need to do that? Maybe you can still have SDCIA
enabled and using CLOSID 15?
-Tony
