On 9/25/26 12:41 AM, 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.
>
> Suggested-by: Kevin Brodsky <[email protected]>
> Suggested-by: Lorenzo Stoakes (ARM) <[email protected]>
> Reviewed-by: Lorenzo Stoakes (ARM) <[email protected]>
> Reviewed-by: Zi Yan <[email protected]>
> Acked-by: David Hildenbrand (Arm) <[email protected]>
> Signed-off-by: Yeoreum Yun <[email protected]>
> ---
> tools/testing/selftests/mm/split_huge_page_test.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c
> b/tools/testing/selftests/mm/split_huge_page_test.c
> index c5d96a4b1db3..ef4058662b91 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -108,6 +108,18 @@ static char *allocate_zero_filled_hugepage(size_t len)
> return result;
> }
>
> +static void disable_khugepaged(void *addr, size_t len)
> +{
> + /*
> + * Disables khugepaged from collapsing THPs in range, existing THP
Should it be "collapsing pages in range into THPs" instead?
> + * pages remain.
> + */
> + if (!madvise(addr, len, MADV_NOHUGEPAGE))
> + return;
> +
> + ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=%d\n", errno);
I feel a ksft_exit_fail_perror() would be better here, since it will
automatically print strerror(errno) as well. Still, it is not something
that should require a respin of its own, so if you plan to respin for
some other changes, you might fold these changes in as well.
Rest looks good, so:
Reviewed-by: Sarthak Sharma <[email protected]>
> +}
> +
> static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int
> nr_hpages, size_t len)
> {
> unsigned long rss_anon_before, rss_anon_after;
> @@ -120,6 +132,8 @@ 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");
>
> + disable_khugepaged(one_page, len);
> +
> /* split all THPs */
> write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> (uint64_t)one_page + len, 0);
> @@ -167,6 +181,8 @@ static void split_pmd_thp_to_order(int order)
> if (!check_huge_anon(one_page, 4 * pmd_pagesize, 4, pmd_pagesize))
> ksft_exit_fail_msg("No THP is allocated\n");
>
> + disable_khugepaged(one_page, len);
> +
> /* split all THPs */
> write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> (uint64_t)one_page + len, order);
> @@ -215,6 +231,8 @@ static void split_pte_mapped_thp(void)
> goto out;
> }
>
> + disable_khugepaged(thp_area, thp_area_size);
> +
> /*
> * To challenge spitting code, we will mremap a single page of each
> * THP (page[i] of thp[i]) in the thp_area into page_area. This will
> @@ -482,6 +500,7 @@ static int create_pagecache_thp_and_fd(const char
> *testfile, size_t fd_size,
> ksft_test_result_skip("Pagecache folio split skipped\n");
> return -2;
> }
> + disable_khugepaged(*addr, fd_size);
> return 0;
> err_out_close:
> close(*fd);
>
