linux-kernel - Re: [PATCH v3] mm: mincore: use pte_batch

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Message-ID: <653bd82d-6c61-4114-bbae-a5f79e811a43@linux.alibaba.com>
Date: Fri, 9 May 2025 15:38:12 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org, david@...hat.com
Cc: 21cnbao@...il.com, ryan.roberts@....com, ziy@...dia.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: mincore: use pte_batch_bint() to batch process
 large folios



On 2025/5/9 15:30, Dev Jain wrote:
> 
> 
> On 09/05/25 6:15 am, Baolin Wang wrote:
>> When I tested the mincore() syscall, I observed that it takes longer with
>> 64K mTHP enabled on my Arm64 server. The reason is the 
>> mincore_pte_range()
>> still checks each PTE individually, even when the PTEs are contiguous,
>> which is not efficient.
>>
>> Thus we can use pte_batch_hint() to get the batch number of the present
>> contiguous PTEs, which can improve the performance. I tested the 
>> mincore()
>> syscall with 1G anonymous memory populated with 64K mTHP, and observed an
>> obvious performance improvement:
>>
>> w/o patch        w/ patch        changes
>> 6022us            549us            +91%
>>
>> Moreover, I also tested mincore() with disabling mTHP/THP, and did not
>> see any obvious regression for base pages.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> 
> Nit: The subject line - s/pte_batch_bint()/pte_batch_hint()

Ah, fat finger. Hope Andrew can help to fix it:)

> Otherwise LGTM
> 
> Reviewed-by: Dev Jain <dev.jain@....com>

Thanks.