linux-kernel - Re: [PATCH v5 2/7] mm: Optimize mprotect() for MM_CP_PROT

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Message-ID: <463ADA54-E6CB-4B63-B306-E108E303F07C@nvidia.com>
Date: Wed, 23 Jul 2025 10:25:52 -0400
From: Zi Yan <ziy@...dia.com>
To: Dev Jain <dev.jain@....com>
Cc: akpm@...ux-foundation.org, ryan.roberts@....com, david@...hat.com,
 willy@...radead.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 catalin.marinas@....com, will@...nel.org, Liam.Howlett@...cle.com,
 lorenzo.stoakes@...cle.com, vbabka@...e.cz, jannh@...gle.com,
 anshuman.khandual@....com, peterx@...hat.com, joey.gouly@....com,
 ioworker0@...il.com, baohua@...nel.org, kevin.brodsky@....com,
 quic_zhenhuah@...cinc.com, christophe.leroy@...roup.eu,
 yangyicong@...ilicon.com, linux-arm-kernel@...ts.infradead.org,
 hughd@...gle.com, yang@...amperecomputing.com
Subject: Re: [PATCH v5 2/7] mm: Optimize mprotect() for MM_CP_PROT_NUMA by
 batch-skipping PTEs

On 18 Jul 2025, at 5:02, Dev Jain wrote:

> For the MM_CP_PROT_NUMA skipping case, observe that, if we skip an
> iteration due to the underlying folio satisfying any of the skip
> conditions, then for all subsequent ptes which map the same folio, the
> iteration will be skipped for them too. Therefore, we can optimize
> by using folio_pte_batch() to batch skip the iterations.
>
> Use prot_numa_skip() introduced in the previous patch to determine whether
> we need to skip the iteration. Change its signature to have a double
> pointer to a folio, which will be used by mprotect_folio_pte_batch() to
> determine the number of iterations we can safely skip.
>
> Signed-off-by: Dev Jain <dev.jain@....com>
> ---
>  mm/mprotect.c | 55 +++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 42 insertions(+), 13 deletions(-)
>
LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi