linux-kernel - Re: [PATCH v1 1/2] mm/page_alloc: conditionally split > pageblock_order pages in free_one_page() and move_freepages_block

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Message-ID: <20245acc-1d2e-4166-ab78-6b1614d4e47c@redhat.com>
Date: Tue, 10 Dec 2024 10:39:44 +0100
From: David Hildenbrand <david@...hat.com>
To: Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
 Johannes Weiner <hannes@...xchg.org>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
 Zi Yan <ziy@...dia.com>, Yu Zhao <yuzhao@...gle.com>
Subject: Re: [PATCH v1 1/2] mm/page_alloc: conditionally split >
 pageblock_order pages in free_one_page() and move_freepages_block_isolate()

On 09.12.24 20:01, Vlastimil Babka wrote:
> On 12/6/24 10:59, David Hildenbrand wrote:
>> Let's special-case for the common scenarios that:
>>
>> (a) We are freeing pages <= pageblock_order
>> (b) We are freeing a page <= MAX_PAGE_ORDER and all pageblocks match
>>      (especially, no mixture of isolated and non-isolated pageblocks)
> 
> Well in many of those cases we could also just adjust the pageblocks... But
> perhaps they indeed shouldn't differ in the first place, unless there's an
> isolation attempt.

Thanks for the review and finding that one flaw.

Yes, I agree: usually we expect this to only happen with isolated 
pageblocks. At least in the scenarios I have in mind (boot, hotplug, 
alloc_contig_range()), we should only ever have a mixture of isolated 
and !isolated.

Maybe one could even special case on zone->nr_isolate_pageblock: if 0, 
just assume all pageblocks are the equal. I'll look into some details 
and might send a follow-up patch.

-- 
Cheers,

David / dhildenb