Re: [PATCH v8 08/24] x86/resctrl: Track the number of dirty RMID a CLOSID has

Moger, Babu
2024-01-03T19:43:06Z

On 12/15/23 11:43, James Morse wrote:
> MPAM's PMG bits extend its PARTID space, meaning the same PMG value can be
> used for different control groups.
>
> This means once a CLOSID is allocated, all its monitoring ids may still be
> dirty, and held in limbo.
>
> Keep track of the number of RMID held in limbo each CLOSID has. This will
> allow a future helper to find the 'cleanest' CLOSID when allocating.
>
> The array is only needed when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is
> defined. This will never be the case on x86.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Tested-by: Babu Moger <babu.moger@amd.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reviewed-by: Babu Moger <babu.moger@amd.com>

> ---
> Changes since v4:
> * Moved closid_num_dirty_rmid[] update under entry->busy check
> * Take the mutex in dom_data_init() as the caller doesn't.
>
> Changes since v5:
> * Added braces after an else.
> * Made closid_num_dirty_rmid an unsigned int.
> * Moved mutex_lock() in dom_data_init() to cover the whole function.
>
> Changes since v6:
> * Made closid_num_dirty_rmid[] and associated tmp variables u32.
>
> Changes since v7:
> * Clobber kfree()d variable with NULL.
> * Guard the use of closid_num_dirty_rmid with IS_ENABLED() so it can be
> optimised out on x86.
> ---
> arch/x86/kernel/cpu/resctrl/monitor.c | 69 +++++++++++++++++++++++----
> 1 file changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 1f371b108a74..6dfc68c800c8 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -50,6 +50,13 @@ struct rmid_entry {
> */
> static LIST_HEAD(rmid_free_lru);
>
> +/**
> + * @closid_num_dirty_rmid The number of dirty RMID each CLOSID has.
> + * Only allocated when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is defined.
> + * Indexed by CLOSID. Protected by rdtgroup_mutex.
> + */
> +static u32 *closid_num_dirty_rmid;
> +
> /*
> * @rmid_limbo_count - count of currently unused but (potentially)
> * dirty RMIDs.
> @@ -292,6 +299,17 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> return 0;
> }
>
> +static void limbo_release_entry(struct rmid_entry *entry)
> +{
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> + rmid_limbo_count--;
> + list_add_tail(&entry->list, &rmid_free_lru);
> +
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> + closid_num_dirty_rmid[entry->closid]--;
> +}
> +
> /*
> * Check the RMIDs that are marked as busy for this domain. If the
> * reported LLC occupancy is below the threshold clear the busy bit and
> @@ -328,10 +346,8 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
>
> if (force_free || !rmid_dirty) {
> clear_bit(idx, d->rmid_busy_llc);
> - if (!--entry->busy) {
> - rmid_limbo_count--;
> - list_add_tail(&entry->list, &rmid_free_lru);
> - }
> + if (!--entry->busy)
> + limbo_release_entry(entry);
> }
> cur_idx = idx + 1;
> }
> @@ -398,6 +414,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> u64 val = 0;
> u32 idx;
>
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> idx = resctrl_arch_rmid_idx_encode(entry->closid, entry->rmid);
>
> entry->busy = 0;
> @@ -423,10 +441,13 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> }
> put_cpu();
>
> - if (entry->busy)
> + if (entry->busy) {
> rmid_limbo_count++;
> - else
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> + closid_num_dirty_rmid[entry->closid]++;
> + } else {
> list_add_tail(&entry->list, &rmid_free_lru);
> + }
> }
>
> void free_rmid(u32 closid, u32 rmid)
> @@ -792,13 +813,33 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
> static int dom_data_init(struct rdt_resource *r)
> {
> u32 idx_limit = resctrl_arch_system_num_rmid_idx();
> + u32 num_closid = resctrl_arch_get_num_closid(r);
> struct rmid_entry *entry = NULL;
> + int err = 0, i;
> u32 idx;
> - int i;
> +
> + mutex_lock(&rdtgroup_mutex);
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
> + u32 *tmp;
> +
> + tmp = kcalloc(num_closid, sizeof(*tmp), GFP_KERNEL);
> + if (!tmp) {
> + err = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + closid_num_dirty_rmid = tmp;
> + }
>
> rmid_ptrs = kcalloc(idx_limit, sizeof(struct rmid_entry), GFP_KERNEL);
> - if (!rmid_ptrs)
> - return -ENOMEM;
> + if (!rmid_ptrs) {
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
> + kfree(closid_num_dirty_rmid);
> + closid_num_dirty_rmid = NULL;
> + }
> + err = -ENOMEM;
> + goto out_unlock;
> + }
>
> for (i = 0; i < idx_limit; i++) {
> entry = &rmid_ptrs[i];
> @@ -818,13 +859,21 @@ static int dom_data_init(struct rdt_resource *r)
> entry = __rmid_entry(idx);
> list_del(&entry->list);
>
> - return 0;
> +out_unlock:
> + mutex_unlock(&rdtgroup_mutex);
> +
> + return err;
> }
>
> static void __exit dom_data_exit(struct rdt_resource *r)
> {
> mutex_lock(&rdtgroup_mutex);
>
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
> + kfree(closid_num_dirty_rmid);
> + closid_num_dirty_rmid = NULL;
> + }
> +
> kfree(rmid_ptrs);
> rmid_ptrs = NULL;
>

--
Thanks
Babu Moger