linux-kernel - Re: [RFC PATCH v1 3/7] mm: Hot page tracking and promotion

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Message-ID: <8565f305-f36d-42a4-abf2-24e064067fc3@amd.com>
Date: Fri, 15 Aug 2025 19:46:24 +0530
From: Bharata B Rao <bharata@....com>
To: "Huang, Ying" <ying.huang@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Jonathan.Cameron@...wei.com, dave.hansen@...el.com, gourry@...rry.net,
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Subject: Re: [RFC PATCH v1 3/7] mm: Hot page tracking and promotion

On 15-Aug-25 7:26 AM, Huang, Ying wrote:
> Bharata B Rao <bharata@....com> writes:
> 
>> This introduces a sub-system for collecting memory access
>> information from different sources. It maintains the hotness
>> information based on the access history and time of access.
>>
>> Additionally, it provides per-lowertier-node kernel threads
>> (named kpromoted) that periodically promote the pages that
>> are eligible for promotion.
>>
>> Sub-systems that generate hot page access info can report that
>> using this API:
>>
>> int pghot_record_access(u64 pfn, int nid, int src,
>> 			unsigned long time)
>>
>> @pfn: The PFN of the memory accessed
>> @nid: The accessing NUMA node ID
>> @src: The temperature source (sub-system) that generated the
>>       access info
>> @time: The access time in jiffies
> 
> How will the page hotness information gather with NUMA balancing hint
> page fault be expressed with this interface?

Something like this can be done for reporting accesses detected by
NUMA balancing -
https://lore.kernel.org/linux-mm/20250616133931.206626-5-bharata@amd.com/

However we need to bypass the hot page threshold detection and rate
limiting and have the same or similar functionality implemented within
this patchset.

Regards,
Bharata.