linux-kernel - Re: [PATCH 02/10] cacheinfo: calculate per-CPU data cache size

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Message-ID: <20230920092402.pvqju4knnqkzqfiq@bogus>
Date:   Wed, 20 Sep 2023 10:24:02 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Huang Ying <ying.huang@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Sudeep Holla <sudeep.holla@....com>,
        Arjan Van De Ven <arjan@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Johannes Weiner <jweiner@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH 02/10] cacheinfo: calculate per-CPU data cache size

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/20230920061856.257597-1-ying.huang@intel.com/