Re: [PATCH v3 05/16] cacheinfo: Allow early detection and population of cache attributes

Gavin Shan
2022-06-01T03:27:11Z

Hi Sudeep,

On 5/25/22 4:14 PM, Sudeep Holla wrote:
> Some architecture/platforms may need to setup cache properties very
> early in the boot along with other cpu topologies so that all these
> information can be used to build sched_domains which is used by the
> scheduler.
>
> Allow detect_cache_attributes to be called quite early during the boot.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
> drivers/base/cacheinfo.c | 45 ++++++++++++++++++++++++---------------
> include/linux/cacheinfo.h | 1 +
> 2 files changed, 29 insertions(+), 17 deletions(-)
>

With the comments improved, as below:

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index ed74db18468f..976142f3e81d 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -193,14 +193,8 @@ static int cache_setup_of_node(unsigned int cpu)
> {
> struct device_node *np;
> struct cacheinfo *this_leaf;
> - struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> unsigned int index = 0;
>
> - /* skip if fw_token is already populated */
> - if (this_cpu_ci->info_list->fw_token) {
> - return 0;
> - }
> -
> np = of_cpu_device_node_get(cpu);
> if (!np) {
> pr_err("Failed to find cpu%d device node\n", cpu);
> @@ -236,6 +230,18 @@ int __weak cache_setup_acpi(unsigned int cpu)
>
> unsigned int coherency_max_size;
>
> +static int cache_setup_properties(unsigned int cpu)
> +{
> + int ret = 0;
> +
> + if (of_have_populated_dt())
> + ret = cache_setup_of_node(cpu);
> + else if (!acpi_disabled)
> + ret = cache_setup_acpi(cpu);
> +
> + return ret;
> +}
> +
> static int cache_shared_cpu_map_setup(unsigned int cpu)
> {
> struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> @@ -246,21 +252,21 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
> if (this_cpu_ci->cpu_map_populated)
> return 0;
>
> - if (of_have_populated_dt())
> - ret = cache_setup_of_node(cpu);
> - else if (!acpi_disabled)
> - ret = cache_setup_acpi(cpu);
> -
> - if (ret)
> - return ret;
> + /*
> + * skip setting up cache properties if LLC is valid, just need
> + * to update the shared cpu_map if the cache attributes were
> + * populated early before all the cpus are brought online
> + */
> + if (!last_level_cache_is_valid(cpu)) {
> + ret = cache_setup_properties(cpu);
> + if (ret)
> + return ret;
> + }
>
> for (index = 0; index < cache_leaves(cpu); index++) {
> unsigned int i;
>
> this_leaf = per_cpu_cacheinfo_idx(cpu, index);
> - /* skip if shared_cpu_map is already populated */
> - if (!cpumask_empty(&this_leaf->shared_cpu_map))
> - continue;
>
> cpumask_set_cpu(cpu, &this_leaf->shared_cpu_map);
> for_each_online_cpu(i) {
> @@ -330,10 +336,13 @@ int __weak populate_cache_leaves(unsigned int cpu)
> return -ENOENT;
> }
>
> -static int detect_cache_attributes(unsigned int cpu)
> +int detect_cache_attributes(unsigned int cpu)
> {
> int ret;
>
> + if (per_cpu_cacheinfo(cpu)) /* Already setup */
> + goto update_cpu_map;
> +
> if (init_cache_level(cpu) || !cache_leaves(cpu))
> return -ENOENT;
>

Here it might be worthy to explain when CPU's cache info has been
populated, by mentioning CPU info can be populated at booting
and hot-add time.

> @@ -349,6 +358,8 @@ static int detect_cache_attributes(unsigned int cpu)
> ret = populate_cache_leaves(cpu);
> if (ret)
> goto free_ci;
> +
> +update_cpu_map:
> /*
> * For systems using DT for cache hierarchy, fw_token
> * and shared_cpu_map will be set up here only if they are
> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> index 7e429bc5c1a4..00b7a6ae8617 100644
> --- a/include/linux/cacheinfo.h
> +++ b/include/linux/cacheinfo.h
> @@ -84,6 +84,7 @@ int populate_cache_leaves(unsigned int cpu);
> int cache_setup_acpi(unsigned int cpu);
> bool last_level_cache_is_valid(unsigned int cpu);
> bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y);
> +int detect_cache_attributes(unsigned int cpu);
> #ifndef CONFIG_ACPI_PPTT
> /*
> * acpi_find_last_cache_level is only called on ACPI enabled
>

Thanks,
Gavin