linux-kernel - Re: [PATCH] mm: Skip the reserved bootmem for compaction

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Message-ID: <f86cf28c-c274-4ba9-8a4d-8d221ad94d62@redhat.com>
Date: Tue, 3 Sep 2024 11:56:29 +0200
From: David Hildenbrand <david@...hat.com>
To: Rong Qianfeng <11065417@...o.com>
Cc: opensource.kernel@...o.com, Rong Qianfeng <rongqianfeng@...o.com>,
 vbabka@...e.cz, mgorman@...hsingularity.net,
 Andrew Morton <akpm@...ux-foundation.org>, Mike Rapoport <rppt@...nel.org>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Skip the reserved bootmem for compaction

On 03.09.24 09:14, Rong Qianfeng wrote:
> Hi David,
> 
> Thanks very much for the detailed comments and explanations!
> 
> 在 2024/9/2 21:45, David Hildenbrand 写道:
>> On 02.09.24 14:24, Rong Qianfeng wrote:
>>> Reserved pages are basically non-lru pages. This kind of memory can't be
>>> used as migration sources and targets, skip it can bring some
>>> performance
>>> benefits.
>>
>> Any numbers? :)
> 
> I am still thinking about how to design test cases. If you have any good
> suggestions,  please tell me. Thank you very much.

Well, you claim that it can bring performance improvement, so it's your 
responsibility to prove it :)

I have real idea how you could measure that, sorry.

This change will make the code more complicated (and as raised, there 
are some corner cases not handled yet). So it's better worth the price. :)

[...]

> 
>>
>>
>> What about free_reserved_page() ? There might be more, though
>> (kimage_free_pages()). You have to take a look at all functions where we
>> clear PageReserved.
> 
> Thanks for your reminder, I found that I missed a lot of functions.
> Maybe a better choice is to clear PB_migrate_skip in free_reserved_page()
> to reduce the amount of modification.

Hm, maybe. At least for free_reserved_area() it would be beneficial to 
minimize the per-page handling.

-- 
Cheers,

David / dhildenb