linux-kernel - Re: [PATCH v2 3/3] selftests/mm/charge_reserved_hugetlb: fix hugetlbfs mount size for large hugepages

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Message-ID: <CAEemH2f67p=wqGrwYnoVCP1fR82xxwJv1xfbMmFrvNaP7LZJog@mail.gmail.com>
Date: Sun, 21 Dec 2025 17:44:22 +0800
From: Li Wang <liwang@...hat.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: akpm@...ux-foundation.org, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Mark Brown <broonie@...nel.org>, Shuah Khan <shuah@...nel.org>, Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v2 3/3] selftests/mm/charge_reserved_hugetlb: fix
 hugetlbfs mount size for large hugepages

David Hildenbrand (Red Hat) <david@...nel.org> wrote:
> On 12/21/25 09:58, Li Wang wrote:
> > charge_reserved_hugetlb.sh mounts a hugetlbfs instance at /mnt/huge with
> > a fixed size of 256M. On systems with large base hugepages (e.g. 512MB),
> > this is smaller than a single hugepage, so the hugetlbfs mount ends up
> > with effectively zero capacity (often visible as size=0 in mount output).
> >
> > As a result, write_to_hugetlbfs fails with ENOMEM and the test can hang
> > waiting for progress.
>
> I'm curious, what's the history of using "256MB" in the first place (or
> specifying any size?).

Seems the script initializes it with "256MB" from:

commit 29750f71a9b4cfae57cdddfbd8ca287eddca5503
Author: Mina Almasry <almasrymina@...gle.com>
Date:   Wed Apr 1 21:11:38 2020 -0700

    hugetlb_cgroup: add hugetlb_cgroup reservation tests


-- 
Regards,
Li Wang