linux-kernel - Re: [PATCH v3 1/5] mm: Optimize mprotect() by batch-skipping PTEs

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Message-ID: <d72c77b7-2f40-4236-8288-e811f82671c6@redhat.com>
Date: Wed, 4 Jun 2025 13:44:18 +0200
From: David Hildenbrand <david@...hat.com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org
Cc: ryan.roberts@....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, ziy@...dia.com
Subject: Re: [PATCH v3 1/5] mm: Optimize mprotect() by batch-skipping PTEs

On 04.06.25 12:38, Dev Jain wrote:
> 
> On 22/05/25 9:48 pm, David Hildenbrand wrote:
>> On 22.05.25 09:47, Dev Jain wrote:
>>>
>>> On 22/05/25 12:43 pm, David Hildenbrand wrote:
>>>>
>>>>>> ... likely with a better function name,
>>>>>
>>>>>
>>>>> I want to be able to reuse the folio from vm_normal_folio(), and we
>>>>> also
>>>>> need
>>>>>
>>>>> nr_ptes to know how much to skip, so if there is no objection in
>>>>> passing
>>>>> int *nr_ptes,
>>>>>
>>>>> or struct folio **foliop to this new function, then I'll carry on with
>>>>> your suggestion :)
>>>>
>>>> Can you quickly prototype what you have in mind and paste it here?
>>>> Will make it easier :)
>>>
>>>
>>> if (prot_numa)
>>>
>>>        func(vma, addr, oldpte, &nr);
>>
>> I'd probably return "nr_ptes" and return the folio using a &folio
>> instead.
>>
>> That way, you can easily extend the function to return the folio in
>> the patch where you really need it (not this patch IIUR :) )
> 
> Just confirming, you mean to return nr_ptes and get the folio by passing
> &folio, and the function parameter will be struct folio **foliop?

Yes.

-- 
Cheers,

David / dhildenb