Re: [RESEND PATCH v7 10/10] selftests/mm/cow: Add tests for anonymous small-sized THP

[Ryan Roberts <ryan.roberts@arm.com>]

On 22/11/2023 16:29, Ryan Roberts wrote:
> Add tests similar to the existing PMD-sized THP tests, but which operate
> on memory backed by (PTE-mapped) small-sized THP. This reuses all the
> existing infrastructure. If the test suite detects that small-sized THP
> is not supported by the kernel, the new tests are skipped.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>  tools/testing/selftests/mm/cow.c | 71 +++++++++++++++++++++++++++++++-
>  1 file changed, 70 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
> index d03c453cfd5c..3efc395c7077 100644
> --- a/tools/testing/selftests/mm/cow.c
> +++ b/tools/testing/selftests/mm/cow.c
> @@ -29,15 +29,49 @@
>  #include "../../../../mm/gup_test.h"
>  #include "../kselftest.h"
>  #include "vm_util.h"
> +#include "thp_settings.h"
> 
>  static size_t pagesize;
>  static int pagemap_fd;
>  static size_t pmdsize;
> +static int nr_thpsmallsizes;
> +static size_t thpsmallsizes[20];

Off the back of some comments David made againt the previous patch [1], I'm
proposing to rework this a bit so that ALL thp sizes are stored in this array,
not just the non-PMD-sized sizes. This makes the changes overall a bit smaller
and easier to understand, I think...

>  static int nr_hugetlbsizes;
>  static size_t hugetlbsizes[10];
>  static int gup_fd;
>  static bool has_huge_zeropage;
> 
> +static int sz2ord(size_t size)
> +{
> +	return __builtin_ctzll(size / pagesize);
> +}
> +
> +static int detect_smallthp_sizes(size_t sizes[], int max)

This changes to detect_thp_sizes() and deposits all sizes in sizes[]

> +{
> +	int count = 0;
> +	unsigned long orders;
> +	size_t kb;
> +	int i;
> +
> +	/* thp not supported at all. */
> +	if (!pmdsize)
> +		return 0;
> +
> +	orders = thp_supported_orders();
> +
> +	/* Only interested in small-sized THP (less than PMD-size). */
> +	for (i = 0; i < sz2ord(pmdsize); i++) {
> +		if (!(orders & (1UL << i)))
> +			continue;
> +		kb = (pagesize >> 10) << i;
> +		sizes[count++] = kb * 1024;
> +		ksft_print_msg("[INFO] detected small-sized THP size: %zu KiB\n",
> +			       kb);

This just prints "[INFO] detected THP size: %zu KiB"

> +	}
> +
> +	return count;
> +}
> +
>  static void detect_huge_zeropage(void)
>  {
>  	int fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page",
> @@ -1113,6 +1147,23 @@ static void run_anon_test_case(struct test_case const *test_case)
>  		run_with_partial_mremap_thp(test_case->fn, test_case->desc, pmdsize);
>  		run_with_partial_shared_thp(test_case->fn, test_case->desc, pmdsize);
>  	}
> +	for (i = 0; i < nr_thpsmallsizes; i++) {
> +		size_t size = thpsmallsizes[i];
> +		struct thp_settings settings = *thp_current_settings();
> +
> +		settings.hugepages[sz2ord(pmdsize)].enabled = THP_NEVER;
> +		settings.hugepages[sz2ord(size)].enabled = THP_ALWAYS;
> +		thp_push_settings(&settings);
> +
> +		run_with_pte_mapped_thp(test_case->fn, test_case->desc, size);
> +		run_with_pte_mapped_thp_swap(test_case->fn, test_case->desc, size);
> +		run_with_single_pte_of_thp(test_case->fn, test_case->desc, size);
> +		run_with_single_pte_of_thp_swap(test_case->fn, test_case->desc, size);
> +		run_with_partial_mremap_thp(test_case->fn, test_case->desc, size);
> +		run_with_partial_shared_thp(test_case->fn, test_case->desc, size);
> +
> +		thp_pop_settings();
> +	}

This same loop covers the pmdsize tests too, and I've just added a conditional
that runs the 2 extra tests that are pmdsize only.

>  	for (i = 0; i < nr_hugetlbsizes; i++)
>  		run_with_hugetlb(test_case->fn, test_case->desc,
>  				 hugetlbsizes[i]);
> @@ -1134,6 +1185,7 @@ static int tests_per_anon_test_case(void)
> 
>  	if (pmdsize)
>  		tests += 8;
> +	tests += 6 * nr_thpsmallsizes;
>  	return tests;
>  }
> 
> @@ -1691,12 +1743,24 @@ static int tests_per_non_anon_test_case(void)
>  int main(int argc, char **argv)
>  {
>  	int err;
> +	struct thp_settings default_settings;
> 
>  	pagesize = getpagesize();
>  	pmdsize = read_pmd_pagesize();
> -	if (pmdsize)
> +	if (pmdsize) {
> +		/* Only if THP is supported. */
> +		thp_read_settings(&default_settings);
> +		default_settings.hugepages[sz2ord(pmdsize)].enabled = THP_GLOBAL;
> +		thp_save_settings();
> +		thp_push_settings(&default_settings);
> +
>  		ksft_print_msg("[INFO] detected PMD-mapped THP size: %zu KiB\n",
>  			       pmdsize / 1024);
> +
> +		nr_thpsmallsizes = detect_smallthp_sizes(thpsmallsizes,
> +						    ARRAY_SIZE(thpsmallsizes));
> +	}
> +
>  	nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,
>  						    ARRAY_SIZE(hugetlbsizes));
>  	detect_huge_zeropage();
> @@ -1715,6 +1779,11 @@ int main(int argc, char **argv)
>  	run_anon_thp_test_cases();
>  	run_non_anon_test_cases();
> 
> +	if (pmdsize) {
> +		/* Only if THP is supported. */
> +		thp_restore_settings();
> +	}
> +
>  	err = ksft_get_fail_cnt();
>  	if (err)
>  		ksft_exit_fail_msg("%d out of %d tests failed\n",
> --
> 2.25.1
>