Re: [PATCH] selftests/mm: add THP sysfs interface test

[Breno Leitao <leitao@debian.org>]

On Mon, Mar 16, 2026 at 12:55:13PM +0000, Lorenzo Stoakes (Oracle) wrote:
> On Mon, Mar 09, 2026 at 05:00:34AM -0700, Breno Leitao wrote:
> > Add a shell-based selftest that exercises the full set of THP sysfs
> > knobs: enabled (global and per-size anon), defrag, use_zero_page,
> > hpage_pmd_size, shmem_enabled (global and per-size), shrink_underused,
> > khugepaged/ tunables, and per-size stats files.
> >
> > Each writable knob is tested for valid writes, invalid-input rejection,
> > idempotent writes, and mode transitions where applicable. All original
> > values are saved before testing and restored afterwards.
> >
> > The test uses the kselftest KTAP framework (ktap_helpers.sh) for
> > structured TAP 13 output, making results parseable by the kselftest
> > harness. The test plan is printed at the end since the number of test
> > points is dynamic (depends on available hugepage sizes and sysfs files).
> >
> > This is particularly useful for validating the refactoring of
> > enabled_store() and anon_enabled_store() to use sysfs_match_string()
> > and the new change_enabled()/change_anon_orders() helpers.
> >
> > Signed-off-by: Breno Leitao <leitao@debian.org>
> 
> The test is broken locally for me, returning error code 127.
> 
> I do appreciate the effort here, so I'm sorry to push back negatively, but I
> feel a bash script here is pretty janky, and frankly if any of these interfaces
> were as broken as this it'd be a major failure that would surely get picked up
> far sooner elsewhere.
> 
> So while I think this might be useful as a local test for your sysfs interface
> changes, I don't think this is really suited to the mm selftests.

That is totally fine. This test is what I have been using to test the
changes, and I decide to share it in case someone find it useful.

Let's drop it.