Re: [PATCH v3 04/16] cacheinfo: Add support to check if last level cache(LLC) is valid or shared

Gavin Shan
2022-06-01T03:22:19Z

Hi Sudeep,

On 5/25/22 4:14 PM, Sudeep Holla wrote:
> It is useful to have helper to check if the given two CPUs share last level
> cache. We can do that check by comparing fw_token or by comparing the cache
> ID. Currently we check just for fw_token as the cache ID is optional.
>
> This helper can be used to build the llc_sibling during arch specific
> topology parsing and feeding information to the sched_domains. This also
> helps to get rid of llc_id in the CPU topology as it is sort of duplicate
> information.
>
> Also add helper to check if the llc information in cacheinfo is valid or not.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
> drivers/base/cacheinfo.c | 26 ++++++++++++++++++++++++++
> include/linux/cacheinfo.h | 2 ++
> 2 files changed, 28 insertions(+)
>

With below nits fixed:

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

> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index 417e1ebf5525..ed74db18468f 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -47,6 +47,32 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
> return sib_leaf->fw_token == this_leaf->fw_token;
> }
>
> +bool last_level_cache_is_valid(unsigned int cpu)
> +{
> + struct cacheinfo *llc;
> +
> + if (!cache_leaves(cpu))
> + return false;
> +
> + llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1);
> +
> + return llc->fw_token;
> +}
> +

return !!llc->fw_token;

> +bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y)
> +{
> + struct cacheinfo *llc_x, *llc_y;
> +
> + if (!last_level_cache_is_valid(cpu_x) ||
> + !last_level_cache_is_valid(cpu_y))
> + return false;
> +
> + llc_x = per_cpu_cacheinfo_idx(cpu_x, cache_leaves(cpu_x) - 1);
> + llc_y = per_cpu_cacheinfo_idx(cpu_y, cache_leaves(cpu_y) - 1);
> +
> + return cache_leaves_are_shared(llc_x, llc_y);
> +}
> +
> #ifdef CONFIG_OF
> /* OF properties to query for a given cache type */
> struct cache_type_info {
> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> index 4ff37cb763ae..7e429bc5c1a4 100644
> --- a/include/linux/cacheinfo.h
> +++ b/include/linux/cacheinfo.h
> @@ -82,6 +82,8 @@ struct cpu_cacheinfo *get_cpu_cacheinfo(unsigned int cpu);
> int init_cache_level(unsigned int cpu);
> 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);
> #ifndef CONFIG_ACPI_PPTT
> /*
> * acpi_find_last_cache_level is only called on ACPI enabled
>

Thanks,
Gavin