Re: [PATCH v3 02/19] x86/resctrl: Access per-rmid structures by index

Ilpo Järvinen
2023-03-21T10:57:31Z

On Mon, 20 Mar 2023, James Morse wrote:

> Because of the differences between Intel RDT/AMD QoS and Arm's MPAM
> monitors, RMID values on arm64 are not unique unless the CLOSID is
> also included. Bitmaps like rmid_busy_llc need to be sized by the
> number of unique entries for this resource.
>
> Add helpers to encode/decode the CLOSID and RMID to an index. The
> domain's rmid_busy__llc and the rmid_ptrs[] array are then sized by
> index, as are the domain mbm_local and mbm_total arrays.
> On x86, the index is always just the RMID, so all these structures
> remain the same size.
>
> The index gives resctrl a unique value it can use to store monitor
> values, and allows MPAM to decode the closid when reading the hardware
> counters.
>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since v1:
> * Added X86_BAD_CLOSID macro to make it clear what this value means
> * Added second WARN_ON() for closid checking, and made both _ONCE()
>
> Changes since v2:
> * Added RESCTRL_RESERVED_CLOSID
> * Removed a newline
> * Repharsed some comments
> * Renamed a variable 'ignore'd
> * Moved X86_RESCTRL_BAD_CLOSID to a previous patch
> ---

> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index cbe986d23df6..3ca40be41a0a 100644

> @@ -732,19 +759,20 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
>
> static int dom_data_init(struct rdt_resource *r)
> {
> + u32 nr_idx = resctrl_arch_system_num_rmid_idx();

You've used idx_limit elsewhere so this name should be consistent with the
others.

--
i.

> struct rmid_entry *entry = NULL;
> - int i, nr_rmids;
> + u32 idx;
> + int i;
>
> - nr_rmids = r->num_rmid;
> - rmid_ptrs = kcalloc(nr_rmids, sizeof(struct rmid_entry), GFP_KERNEL);
> + rmid_ptrs = kcalloc(nr_idx, sizeof(struct rmid_entry), GFP_KERNEL);
> if (!rmid_ptrs)
> return -ENOMEM;
>
> - for (i = 0; i < nr_rmids; i++) {
> + for (i = 0; i < nr_idx; i++) {
> entry = &rmid_ptrs[i];
> INIT_LIST_HEAD(&entry->list);
>
> - entry->rmid = i;
> + resctrl_arch_rmid_idx_decode(i, &entry->closid, &entry->rmid);
> list_add_tail(&entry->list, &rmid_free_lru);
> }
>
> @@ -753,7 +781,8 @@ static int dom_data_init(struct rdt_resource *r)
> * default_rdtgroup control group, which will be setup later. See
> * rdtgroup_setup_root().
> */
> - entry = __rmid_entry(0, 0);
> + idx = resctrl_arch_rmid_idx_encode(RESCTRL_RESERVED_CLOSID, 0);
> + entry = __rmid_entry(idx);
> list_del(&entry->list);
>
> return 0;