linux-kernel - Re: [RFC PATCH v1 0/4] Kernel thread based async batch migration

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Message-ID: <87zfe220o7.fsf@DESKTOP-5N7EMDA>
Date: Fri, 20 Jun 2025 17:59:52 +0800
From: "Huang, Ying" <ying.huang@...ux.alibaba.com>
To: Bharata B Rao <bharata@....com>
Cc: linux-kernel@...r.kernel.org,  linux-mm@...ck.org,
  Jonathan.Cameron@...wei.com,  dave.hansen@...el.com,  gourry@...rry.net,
  hannes@...xchg.org,  mgorman@...hsingularity.net,  mingo@...hat.com,
  peterz@...radead.org,  raghavendra.kt@....com,  riel@...riel.com,
  rientjes@...gle.com,  sj@...nel.org,  weixugc@...gle.com,
  willy@...radead.org,  ziy@...dia.com,  dave@...olabs.net,
  nifan.cxl@...il.com,  xuezhengchu@...wei.com,  yiannis@...corp.com,
  akpm@...ux-foundation.org,  david@...hat.com
Subject: Re: [RFC PATCH v1 0/4] Kernel thread based async batch migration

Bharata B Rao <bharata@....com> writes:

> On 20-Jun-25 12:09 PM, Huang, Ying wrote:
>> Bharata B Rao <bharata@....com> writes:
>> <snip>
>> 
>> I don't think page flag + scanning is a good idea.If the
>
> If extended page flags is not the ideal location (I chose it in this
> version only to get something going quickly), we can look at maintaining
> per-pfn allocation for the required hot page metadata separately.
>
> Or is your concern specifically with scanning? What problems do you
> see?
>
> It is the cost or the possibility of not identifying the migrate-ready
> pages in time? Or something else??

We may need to scan a large number of pages to identify a page to
promote.  This will waste CPU cycles and pollute cache.

---
Best Regards,
Huang, Ying