Re: [PATCH v2 3/3] mm/khugepaged: release contended mmap read lock after scanning enough VMAs

[Jose A. Perez de Azpillaga]

On 11/6/26 11:33 AM, Lorenzo Stoakes (ARM) wrote:
> On Fri, Nov 06, 2026 at 11:29:00AM +0100, Jose A. Perez de Azpillaga wrote:
>>>> with pages_to_scan below 4 the batch is 0, so under constant contention
>>>> we keep dropping the lock at the cursor and never scan anything, don't we?
>>>
>>> This feels like repackaged AI review...
>>>
>>> The mmap lock won't be eternally contended and if it is, with pages_to_scan
>>> under 4, I think that's fine.
>>>
>>> Alternatively could make that >= an == and the post-++ a pre-++ and the 0 will
>>> never be hit in this case.
>>>
>>> Or could have a minimum cap.
>>
>> with >= a minimum cap needs to be 2, since the cursor can stop at hend
>> inside the VMA we just scanned and the walk lands on it again after the
>> drop. with == only batch - 1 VMAs get scanned per cycle, so a batch of 1
>> scans nothing, today's batch-0 loop at pages_to_scan 4..7, and a batch
>> of 2 hits the hend case. it's safe from 3 up.
> 
> Please don't copy/paste LLM responses. I'm sure it's in good faith, but it's not
> helpful. I will run any changes through AI myself.

it wasn't my intention. I am bad at writing reviews, so AI assists me to
reword it, so it's polished, and I still check all the output. now
onward, maybe my reviews get a bit clumsy, and not polished. I will stop
rewording them.

-- 
cheers,
jose a. p-a