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

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Message-ID: <20260120094744.5d92e34a@pumpkin>
Date: Tue, 20 Jan 2026 09:47:44 +0000
From: David Laight <david.laight.linux@...il.com>
To: "Li Zhe" <lizhe.67@...edance.com>
Cc: <david@...nel.org>, <akpm@...ux-foundation.org>,
 <dan.j.williams@...el.com>, <dave@...olabs.net>,
 <ankur.a.arora@...cle.com>, <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>, <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 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).

The only real gain has to come from zeroing pages when the system is idle.
That will give plenty of zeroed pages needed for starting a web browser
from the desktop and also speed up single-threaded things like 'make -j1'.

	David