linux-kernel - Re: [PATCH v1 05/29] mm/balloon_compaction: make PageOffline sticky until the page is freed

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Message-ID: <1618bfb3-fbc2-46c4-954b-f042803cace2@redhat.com>
Date: Tue, 1 Jul 2025 10:12:06 +0200
From: David Hildenbrand <david@...hat.com>
To: Zi Yan <ziy@...dia.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
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 Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH v1 05/29] mm/balloon_compaction: make PageOffline sticky
 until the page is freed

On 30.06.25 18:14, Zi Yan wrote:
> On 30 Jun 2025, at 12:01, Lorenzo Stoakes wrote:
> 
>> On Mon, Jun 30, 2025 at 02:59:46PM +0200, David Hildenbrand wrote:
>>> Let the page freeing code handle clearing the page type.
>>
>> Why is this advantageous? We want to keep the page marked offline for longer?
>>
>>>
>>> Acked-by: Zi Yan <ziy@...dia.com>
>>> Acked-by: Harry Yoo <harry.yoo@...cle.com>
>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>
>> On assumption this UINT_MAX stuff is sane :)) I mean this is straightforward I
>> guess:
> 
> This is how page type is cleared.
> See: https://elixir.bootlin.com/linux/v6.15.4/source/include/linux/page-flags.h#L1013.
> 
> I agree with you that patch 4 should have a comment in free_pages_prepare()
> about what the code is for and why UINT_MAX is used.

I can add a comment

/* Reset the page_type -> _mapcount to -1 */

To patch #4.

-- 
Cheers,

David / dhildenb