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

[Yeoreum Yun <yeoreum.yun@arm.com>]

Hi Sarthak,

> Hi Yeoreum!
> 
> On 9/2/26 11:26 PM, 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
> 
> Nit : pre-existing

Sorry for typo ;)

> 
> > 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.
> > 
> > After this patch, output of transhuge-stress:
> > 
> >   transhuge-stress: allocate 3817 transhuge pages, using 122146 MiB virtual memory and 119 MiB of ram
> >     2.558 s/loop, 0.670 ms/page,  47755.759 MiB/s	2585 succeed, 1232 failed, 2585 different pages
> >     2.640 s/loop, 0.692 ms/page,  46268.432 MiB/s	2585 succeed, 1232 failed, 2585 different pages
> >     2.635 s/loop, 0.690 ms/page,  46360.298 MiB/s	2585 succeed, 1232 failed, 2585 different pages
> >     2.782 s/loop, 0.729 ms/page,  43899.795 MiB/s	2616 succeed, 1201 failed, 2616 different pages
> >     2.692 s/loop, 0.705 ms/page,  45380.876 MiB/s	2627 succeed, 1190 failed, 2627 different pages
> >     2.612 s/loop, 0.684 ms/page,  46765.812 MiB/s	2628 succeed, 1189 failed, 2628 different pages
> >     2.683 s/loop, 0.703 ms/page,  45520.990 MiB/s	2630 succeed, 1187 failed, 2630 different pages
> >     2.727 s/loop, 0.714 ms/page,  44789.321 MiB/s	2631 succeed, 1186 failed, 2631 different pages
> >     ...
> >   ok 1 Completed
> > 
> > Suggested-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > ---
> 
> [...]
> 
> > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> > index 4821a3563036..4332f8fb2104 100644
> > --- a/tools/testing/selftests/mm/vm_util.c
> > +++ b/tools/testing/selftests/mm/vm_util.c
> > @@ -21,6 +21,8 @@
> >  
> >  unsigned int __page_size;
> >  unsigned int __page_shift;
> > +uint64_t __hpage_size;
> > +uint64_t __hpage_shift;
> 
> I was wondering, would it make more sense to call these __pmd_pagesize
> and __pmd_shift instead?
> 
> hpage_size is used at places for mTHPs of arbitrary sizes and these
> values come from read_pmd_pagesize(). So calling __hpage_size as the PMD
> size seems a bit weird. Also, there is already a pmd_pagesize variable
> in vm_util.c, so I feel the PMD specific names would be more consistent.

That seems better. Thanks!

-- 
Sincerely,
Yeoreum Yun