linux-kernel - Re: [PATCH v4] arm64/mm: Optimize loop to reduce redundant operations of contpte_ptep

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Message-ID: <8bdde7df-15d7-4f24-b358-e9ffab0de1d0@redhat.com>
Date: Fri, 9 May 2025 11:25:18 +0200
From: David Hildenbrand <david@...hat.com>
To: Xavier <xavier_qy@....com>
Cc: 21cnbao@...il.com, ryan.roberts@....com, dev.jain@....com,
 ioworker0@...il.com, akpm@...ux-foundation.org, catalin.marinas@....com,
 gshan@...hat.com, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, will@...nel.org, willy@...radead.org,
 ziy@...dia.com
Subject: Re: [PATCH v4] arm64/mm: Optimize loop to reduce redundant operations
 of contpte_ptep_get

On 09.05.25 11:17, Xavier wrote:
> 
> 
> 
> At 2025-05-08 16:30:14, "David Hildenbrand" <david@...hat.com> wrote:
>> On 08.05.25 09:03, Xavier Xia wrote:
>>> This commit optimizes the contpte_ptep_get and contpte_ptep_get_lockless
>>> function by adding early termination logic. It checks if the dirty and
>>> young bits of orig_pte are already set and skips redundant bit-setting
>>> operations during the loop. This reduces unnecessary iterations and
>>> improves performance.
>>>
>>> In order to verify the optimization performance, a test function has been
>>> designed. The function's execution time and instruction statistics have
>>> been traced using perf, and the following are the operation results on a
>>> certain Qualcomm mobile phone chip:
>>
>> For the future, please don't post vN+1 as reply to vN.
> 
> I will pay attention to it when I submit it later. Thank you for the reminder.

The rationale is that many people will just treat it as some discussion 
noise as part of vN and not really have a closer look, waiting for vN+1.

-- 
Cheers,

David / dhildenb