On Wed, Sep 20, 2023 at 02:18:48PM +0800, Huang Ying wrote:
> Per-CPU data cache size is useful information. For example, it can be
> used to determine per-CPU cache size. So, in this patch, the data
> cache size for each CPU is calculated via data_cache_size /
> shared_cpu_weight.
>
> A brute-force algorithm to iterate all online CPUs is used to avoid
> to allocate an extra cpumask, especially in offline callback.
>
You have not mentioned who will use this information ? Looking at the
change, it is not exposed to the user-space. Also I see this is actually
part of the series [1]. Is this info used in any of those patches ? Can you
point me to the same ?
Not all architecture use cacheinfo yet. How will the mm changes affect those
platforms ?
--
Regards,
Sudeep
[1] https://lore.kernel.org/all/[email protected]/
Sudeep Holla <[email protected]> writes:
> On Wed, Sep 20, 2023 at 02:18:48PM +0800, Huang Ying wrote:
>> Per-CPU data cache size is useful information. For example, it can be
>> used to determine per-CPU cache size. So, in this patch, the data
>> cache size for each CPU is calculated via data_cache_size /
>> shared_cpu_weight.
>>
>> A brute-force algorithm to iterate all online CPUs is used to avoid
>> to allocate an extra cpumask, especially in offline callback.
>>
>
> You have not mentioned who will use this information ? Looking at the
> change, it is not exposed to the user-space. Also I see this is actually
> part of the series [1]. Is this info used in any of those patches ? Can you
> point me to the same ?
Yes. It is used by [PATCH 03/10] of the series. If the per-CPU data
cache size is large enough, we will cache more pages in the per-CPU
pageset to reduce the zone lock contention.
> Not all architecture use cacheinfo yet. How will the mm changes affect those
> platforms ?
If cacheinfo isn't available, we will fallback to the original
behavior. That is, we will drain per-CPU pageset more often (that is,
cache less to improve cache-hot pages sharing between CPUs).
> --
> Regards,
> Sudeep
>
> [1] https://lore.kernel.org/all/[email protected]/
--
Best Regards,
Huang, Ying