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Date:   Wed, 19 Apr 2023 05:11:45 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     linux-mm@kvack.org, Kaiyang Zhao <kaiyang2@cs.cmu.edu>,
        Mel Gorman <mgorman@techsingularity.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        David Rientjes <rientjes@google.com>,
        linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [RFC PATCH 00/26] mm: reliable huge page allocator
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References: <20230418191313.268131-1-hannes@cmpxchg.org>
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On Tue, Apr 18, 2023 at 03:12:47PM -0400, Johannes Weiner wrote:
> This series proposes to make THP allocations reliable by enforcing
> pageblock hygiene, and aligning the allocator, reclaim and compaction
> on the pageblock as the base unit for managing free memory. All orders
> up to and including the pageblock are made first-class requests that
> (outside of OOM situations) are expected to succeed without
> exceptional investment by the allocating thread.
> 
> A neutral pageblock type is introduced, MIGRATE_FREE. The first
> allocation to be placed into such a block claims it exclusively for
> the allocation's migratetype. Fallbacks from a different type are no
> longer allowed, and the block is "kept open" for more allocations of
> the same type to ensure tight grouping. A pageblock becomes neutral
> again only once all its pages have been freed.

YES!  This is exactly what I've been thinking is the right solution
for some time.  Thank you for doing it.