Re: [PATCH v2 1/2] kselftest: mm: prevent random failure of huge page split for khugepaged

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

> On 8/26/26 14:24, Yeoreum Yun wrote:
> > There're some random failure for split_huge_page_test when khugepaged
> > collapses pages into pmd again which had split by the test.
> > 
> > Prevent the khugepaged's collapses for split page by setting the
> > mapped pmd-huge-page with MADV_NOHUGEPAGE before split.
> > 
> > Reported-by: Kevin Brodsky <kevin.brodsky@arm.com>
> > Reviewed-by: Zi Yan <ziy@nvidia.com>
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > ---
> >  tools/testing/selftests/mm/split_huge_page_test.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> > index 86a603692826..8f68bc94a5ca 100644
> > --- a/tools/testing/selftests/mm/split_huge_page_test.c
> > +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> > @@ -180,6 +180,10 @@ static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp
> >  	if (!rss_anon_before)
> >  		ksft_exit_fail_msg("No RssAnon is allocated before split\n");
> >  
> > +	/* Prevent khugepaged from collapsing the pages. */
> > +	if (madvise(one_page, len, MADV_NOHUGEPAGE))
> > +		ksft_print_msg("MADV_NOHUGEPAGE failed to prevent khugepaged from collapsing pages.\n");
> > +
> 
> Ok, this is really only expected to fail on extremely old kernels or kernels
> without CONFIG_TRANSPARENT_HUGEPAGE (where we should never get to that point :) ).
> 
> Can we just turn that into a
> 	ksft_exit_fail_perror("madvise(MADV_NOHUGEPAGE)");
> 
> I'm okay with a ksft_print_msg() as well, but would shorten the message quite a
> lot ("MADV_NOHUGEPAGE failed" or sth).

Thanks. I'll change the message only then.

-- 
Sincerely,
Yeoreum Yun