Re: [PATCH v3 1/2] mm: huge_memory: disallow hugepages if the system-wide THP sysfs settings are disabled

[Baolin Wang]

On 2025/6/24 16:29, David Hildenbrand wrote:
> On 24.06.25 03:48, Baolin Wang wrote:
> > On 2025/6/23 21:54, David Hildenbrand wrote:
> > > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/
> > > > selftests/mm/khugepaged.c
> > > > index 4341ce6b3b38..85bfff53dba6 100644
> > > > --- a/tools/testing/selftests/mm/khugepaged.c
> > > > +++ b/tools/testing/selftests/mm/khugepaged.c
> > > > @@ -501,11 +501,7 @@ static void __madvise_collapse(const char *msg,
> > > > char *p, int nr_hpages,
> > > >        printf("%s...", msg);
> > > > -    /*
> > > > -     * Prevent khugepaged interference and tests that MADV_COLLAPSE
> > > > -     * ignores /sys/kernel/mm/transparent_hugepage/enabled
> > > > -     */
> > > > -    settings.thp_enabled = THP_NEVER;
> > > > +    settings.thp_enabled = THP_ALWAYS;
> > >
> > >
> > > Would MADVISE mode also work here? If we don't set MADV_HUGEPAGE, then
> > > khugepaged should be excluded, correct?
> >
> > I tried this, but some test cases failed. As I replied to Barry, it's
> > because some tests previously set MADV_NOHUGEPAGE, and now there is no
> > way to clear the MADV_NOHUGEPAGE flag except by setting MADV_HUGEPAGE.
>
> Okay, can you add that detail to the patch description. 

Sure. Will do.

> I suspect we 
> really want a way to undo what MADV_NOHUGEPAGE/MADV_NOHUGEPAGE did (if 
> only naming wouldn't be complicated: MADV_DEFAULT_HUGEPAGE, hmmmm).