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

[David Hildenbrand (Red Hat)]

On 12/21/25 10:44, Li Wang wrote:
> David Hildenbrand (Red Hat) <david@xxxxxxxxxx> 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@xxxxxxxxxx>
> Date:   Wed Apr 1 21:11:38 2020 -0700
>
>      hugetlb_cgroup: add hugetlb_cgroup reservation tests

What would happen if we don't specify a size at all?

--
Cheers

David