linux-kernel - Re: [PATCH v2 0/8] Introduce a huge-page pre-zeroing mechanism

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Message-ID: <CAGudoHGb1w92gn89BBuMQOmvcVZkwvt8CK8hFtGg3xmHphmiEw@mail.gmail.com>
Date: Wed, 14 Jan 2026 13:11:57 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: Li Zhe <lizhe.67@...edance.com>, akpm@...ux-foundation.org, 
	ankur.a.arora@...cle.com, fvdl@...gle.com, joao.m.martins@...cle.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com, 
	muchun.song@...ux.dev, osalvador@...e.de, raghavendra.kt@....com
Subject: Re: [PATCH v2 0/8] Introduce a huge-page pre-zeroing mechanism

On Wed, Jan 14, 2026 at 12:55 PM David Hildenbrand (Red Hat)
<david@...nel.org> wrote:
> You said "I wonder if implementing hugepage pre-zeroing directly within
> the kernel would be a simpler and more direct way to accelerate VM
> creation".
>
> And I agree. But to make that fly (no user space polling interface), I
> was wondering whether we could do it like "init_on_free" and let whoever
> frees a hugetlb folio just reinitialize it with 0.
>
> No kernel thread, no user space thread involved.
>

i don't see how this is supposed to address the stated problem of
zeroing being incredibly expensive.

With machinery to pre-zero and depending on availability of CPU time +
pages eligible for allocation but not yet zeroed vs vm
startups/teardowns frequency, there is some amount of real time which
wont be spent waiting on said zeroing because it was already done.

Any approach which keeps the overhead with the program allocating the
page can't take advantage of it, even if said overhead is paid at the
end of its life.