Re: [PATCH] kselftest: mm: remove HPAGE_SIZE and HPAGE_SHIFT macro

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Thu, Sep 03, 2026 at 03:46:20PM +0100, Yeoreum Yun wrote:
> > > On Wed, Sep 02, 2026 at 06:56:11PM +0100, Yeoreum Yun wrote:
> > > > HPAGE_SIZE and HPAGE_SHIFT macro is written based on the 4KB PAGE_SIZE.
> > > > When this macro is used in some test, test result would be strange in
> > > > the system where PAGE_SIZE is more than 4KB.
> > > >
> > > > Here is example with transhuge-stress test with 16KB PAGE_SIZE:
> > > >
> > > >   transhuge-stress: allocate 61073 transhuge pages, using 122146 MiB virtual memory and 1908 MiB of ram
> > > >     3.292 s/loop, 0.054 ms/page,  37106.002 MiB/s	2566 succeed, 58507 failed, 2566 different pages
> > > >     0.591 s/loop, 0.010 ms/page, 206850.792 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     0.527 s/loop, 0.009 ms/page, 231895.107 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     0.527 s/loop, 0.009 ms/page, 231839.704 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     0.528 s/loop, 0.009 ms/page, 231544.782 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     0.528 s/loop, 0.009 ms/page, 231462.074 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     0.527 s/loop, 0.009 ms/page, 231770.300 MiB/s	   0 succeed, 61073 failed,    0 different pages
> > > >     ...
> > > >   ok 1 Completed
> > > >
> > > > Remove the HPAGE_SIZE and HPAGE_SHIFT macro. and introduce hpshift()
> > > > helper to get the HPAGE_SHIFT properly. For HPAGE_SIZE, use pre-exist
> > > > helper, read_pmd_pagesize().
> > > >
> > > > Also, do KSM_MERGE_TIME_HUGE_PAGES test with size of 512 MiB which
> > > > is the LCD pmd_size among 4KB, 16KB and 64KB page_size.
> > >
> > > Probably worth spelling out Least Common Denominator for those who might
> > > mistaken this for a kind of display panel :P
> >
> > Bad typo :( LCM (least common multiple) :(
> >
> > >
> > > I also wonder if it's worth pulling that out as a separate patch in a series for
> > > better bisectability?
> >
> > Okay. I'll separate it.
>
> Hmm, I think it would be better to keep the change as is, including the
> updated ksm_tests parameter. Although allocate_transhuge() correctly
> allocates mappings aligned to the PMD page size, `ksm_tests -H -s 100`
> would otherwise fail because 100 MiB is not a multiple of the PMD page
> size.

OK, just add a note about it in the commit msg :)

>
> [...]
>
> --
> Sincerely,
> Yeoreum Yun

--
Cheers, Lorenzo