linux-kernel - Re: [PATCH 0/3] Optimize mremap() by PTE-batching

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Message-ID: <b26480a7-ea81-408a-b287-7cd52571a1d0@arm.com>
Date: Tue, 6 May 2025 14:46:15 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org
Cc: Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, vbabka@...e.cz,
 jannh@...gle.com, pfalcato@...e.de, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, david@...hat.com, peterx@...hat.com,
 ryan.roberts@....com, mingo@...nel.org, libang.li@...group.com,
 maobibo@...ngson.cn, zhengqi.arch@...edance.com, baohua@...nel.org,
 willy@...radead.org, ioworker0@...il.com, yang@...amperecomputing.com
Subject: Re: [PATCH 0/3] Optimize mremap() by PTE-batching

On 5/6/25 10:30, Dev Jain wrote:
> Use PTE batching to optimize mremap().
> 
> Mapping 512K of memory, memsetting it, remapping it to src + 512K, and
> munmapping it 10,000 times, the average execution time reduces from 1.9 to
> 1.2 seconds, giving a 37% performance optimization. (Apple M3)

That's impressive improvement. But could you please re-organize the test
description into a pseudo code format or better provide the test program
itself (which should be compact anyways) just to be more clear about the
scenario where this helps.

> 
> Dev Jain (3):
>   mm: Call pointers to ptes as ptep
>   mm: Add generic helper to hint a large folio
>   mm: Optimize mremap() by PTE batching
> 
>  include/linux/pgtable.h | 16 +++++++++++++++
>  mm/mremap.c             | 44 +++++++++++++++++++++++++++--------------
>  2 files changed, 45 insertions(+), 15 deletions(-)
>