linux-kernel - Re: [RFC 00/12] mm: PUD (1GB) THP implementation

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Message-ID: <a0c6c8d86ea05dcf5ff96a9d48d6ec79948c88ee.camel@surriel.com>
Date: Sun, 01 Feb 2026 21:44:12 -0500
From: Rik van Riel <riel@...riel.com>
To: Usama Arif <usamaarif642@...il.com>, ziy@...dia.com, Andrew Morton
	 <akpm@...ux-foundation.org>, David Hildenbrand <david@...nel.org>, 
	lorenzo.stoakes@...cle.com, linux-mm@...ck.org
Cc: hannes@...xchg.org, shakeel.butt@...ux.dev, kas@...nel.org,
 baohua@...nel.org, 	dev.jain@....com, baolin.wang@...ux.alibaba.com,
 npache@...hat.com, 	Liam.Howlett@...cle.com, ryan.roberts@....com,
 vbabka@...e.cz, 	lance.yang@...ux.dev, linux-kernel@...r.kernel.org,
 kernel-team@...a.com, Frank van der Linden	 <fvdl@...gle.com>
Subject: Re: [RFC 00/12] mm: PUD (1GB) THP implementation

On Sun, 2026-02-01 at 16:50 -0800, Usama Arif wrote:
> 
> 1. Static Reservation: hugetlbfs requires pre-allocating huge pages
> at boot
>    or runtime, taking memory away. This requires capacity planning,
>    administrative overhead, and makes workload orchastration much
> much more
>    complex, especially colocating with workloads that don't use
> hugetlbfs.
> 
To address the obvious objection "but how could we
possibly allocate 1GB huge pages while the workload
is running?", I am planning to pick up the CMA balancing 
patch series (thank you, Frank) and get that in an 
upstream ready shape soon.

https://lkml.org/2025/9/15/1735

That patch set looks like another case where no
amount of internal testing will find every single
corner case, and we'll probably just want to
merge it upstream, deploy it experimentally, and
aggressively deal with anything that might pop up.

With CMA balancing, it would be possibly to just
have half (or even more) of system memory for
movable allocations only, which would make it possible
to allocate 1GB huge pages dynamically.

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