Re: Avoid reading /sys/kernel/mm/transparent_hugepage/?

[H.J. Lu]

On Fri, Apr 10, 2026 at 4:35 PM Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote:
>
> On Fri, Apr 10, 2026 at 03:40:30PM +0800, H.J. Lu wrote:
> > On Fri, Apr 10, 2026 at 3:28 PM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
> > >
> > > * H. J. Lu:
> > >
> > > > To enable THP segment load, ld.so opens and reads 2 files under
> > > > /sys/kernel/mm/transparent_hugepage/.   This requires mounting
> > > > /sys and is expensive.   Is it possible to put such info in vDSO?
> > >
> > > Alexey Dobriyan proposed adding AT_PAGE_SHIFT_LIST to the auxiliary
> >
> > Does it cover
> >
> > [hjl@gnu-tgl-3 linux]$ cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
> > 2097152
> > [hjl@gnu-tgl-3 linux]$
> >
> > > vector a while back, but I don't know the status of that.
>
> Status: nothing happened.
>
> > How can we get
> >
> > [hjl@gnu-tgl-3 linux]$ cat /sys/kernel/mm/transparent_hugepage/enabled
> > always [madvise] never
> > [hjl@gnu-tgl-3 linux]$
>
> This is not covered, see the link:
> https://lore.kernel.org/lkml/ecb049aa-bcac-45c7-bbb1-4612d094935a@p183/
>
> PAGE_SHIFT_MASK should be folded into system call probably.

We need a fast way to check THP status for THP segment load.
A system call to return /sys/kernel/mm/transparent_hugepage/enabled
and /sys/kernel/mm/transparent_hugepage/hpage_pmd_size should
work.

-- 
H.J.