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

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Message-Id: <20260120103949.7673-1-lizhe.67@bytedance.com>
Date: Tue, 20 Jan 2026 18:39:48 +0800
From: "Li Zhe" <lizhe.67@...edance.com>
To: <david.laight.linux@...il.com>
Cc: <akpm@...ux-foundation.org>, <ankur.a.arora@...cle.com>, 
	<dan.j.williams@...el.com>, <dave@...olabs.net>, <david@...nel.org>, 
	<fvdl@...gle.com>, <gourry@...rry.net>, <joao.m.martins@...cle.com>, 
	<jonathan.cameron@...wei.com>, <linux-cxl@...r.kernel.org>, 
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, 
	<lizhe.67@...edance.com>, <mhocko@...e.com>, <mjguzik@...il.com>, 
	<muchun.song@...ux.dev>, <osalvador@...e.de>, <raghavendra.kt@....com>, 
	<wangzhou1@...ilicon.com>, <zhanjie9@...ilicon.com>
Subject: Re: [PATCH v2 0/8] Introduce a huge-page pre-zeroing mechanism

On Tue, 20 Jan 2026 09:47:44 +0000, david.laight.linux@...il.com wrote:

> On Tue, 20 Jan 2026 14:27:06 +0800
> "Li Zhe" <lizhe.67@...edance.com> wrote:
> 
> > In light of the preceding discussion, we appear to have reached the
> > following understanding:
> > 
> > (1) At present we prefer to mitigate slow application startup (e.g.,
> > VM creation) by zeroing huge pages at the moment they are freed
> > (init_on_free). The principal benefit is that user space gains the
> > performance improvement without deploying any additional user space
> > daemon.
> 
> Am I missing something?
> If userspace does:
> $ program_a; program_b
> and pages used by program_a are zeroed when it exits you get the delay
> for zeroing all the pages it used before program_b starts.
> OTOH if the zeroing is deferred program_b only needs to zero the pages
> it needs to start (and there may be some lurking).

Under the init_on-free approach, improving the speed of zeroing may
indeed prove necessary.

However, I believe we should first reach consensus on adopting
“init_on_free” as the solution to slow application startup before
turning to performance tuning.

Thanks,
Zhe