linux-kernel - Re: [PATCH v1 0/2] Free contiguous order-0 pages efficiently

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Message-ID: <7232ac17-8fb4-482b-b820-78d6bd47c4a5@kernel.org>
Date: Mon, 5 Jan 2026 17:26:23 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Ryan Roberts <ryan.roberts@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
 Zi Yan <ziy@...dia.com>, Uladzislau Rezki <urezki@...il.com>,
 "Vishal Moola (Oracle)" <vishal.moola@...il.com>,
 Ackerley Tng <ackerleytng@...gle.com>, Michael Roth <michael.roth@....com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/2] Free contiguous order-0 pages efficiently

On 1/5/26 17:17, Ryan Roberts wrote:
> Hi All,

Hi,

> 
> A recent change to vmalloc caused some performance benchmark regressions (see
> [1]). I'm attempting to fix that (and at the same time signficantly improve
> beyond the baseline) by freeing a contiguous set of order-0 pages as a batch.

I recently raised the utility of something like that in case we had to 
split a large folio in the page cache for guestmemfd, and then want to 
punch-hole the whole (original) thing while making sure that the whole 
thing ends up back in the buddy.

Freeing individual chunks (e.g., order-0 pages) has the problem that 
some pages might get reallocated before merged, consequently fragmenting 
the bigger chunk.

-- 
Cheers

David