linux-kernel - Re: [PATCH v9 7/8] mm: add folio_put_mgen() to deliver migrc's generation number to pcp or buddy

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Date: Wed, 17 Apr 2024 16:55:55 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Byungchul Park <byungchul@...com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kernel_team@...ynix.com, akpm@...ux-foundation.org,
	ying.huang@...el.com, vernhao@...cent.com,
	mgorman@...hsingularity.net, hughd@...gle.com, david@...hat.com,
	peterz@...radead.org, luto@...nel.org, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	rjgolo@...il.com
Subject: Re: [PATCH v9 7/8] mm: add folio_put_mgen() to deliver migrc's
 generation number to pcp or buddy

On Wed, Apr 17, 2024 at 04:18:46PM +0900, Byungchul Park wrote:
> Introduced a new API, folio_put_mgen(), to deliver migrc's generation
> number to pcp or buddy that will be used by migrc mechanism to track
> need of tlb flush for each page residing in pcp or buddy.
> 
> migrc makes decision whether tlb flush is needed or not, based on a
> generation number stored in the interesting page and the global
> generation number, for that tlb flush required has been completed.
> 
> For now, the delivery works only for the following call path but not for
> e.g. free_the_page(), __free_pages_ok() and free_unref_page_list() that
> are not for releasing source folios during migration:
> 
>    folio_put_mgen()
>       __folio_put_mgen()
> 	__folio_put_small()
> 	   free_unref_page()
> 	      free_unref_page_commit()
> 	      free_one_page()
> 	         __free_one_page()

You're going to want to rebase this on mm-unstable.  __folio_put_small()
went away in "mm: combine __folio_put_small, __folio_put_large and
__folio_put"