Re: [PATCH v4 2/3] kselftest: mm: remove HPAGE_SIZE and HPAGE_SHIFT macro

[Lorenzo Stoakes (ARM)]

On Mon, Sep 21, 2026 at 11:36:39AM +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 then 4KB.
>
> Here is the 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 pmd_pshift()
> helper to get the HPAGE_SHIFT properly. For HPAGE_SIZE, use pre-existing
> helper, pmd_psize().
>
> Also, run the KSM_MERGE_TIME_HUGE_PAGES test with a size of 512 MiB,
> which is the least common multiple of the PMD sizes for 4 KiB, 16 KiB,
> and 64 KiB base pages. Since allocate_transhuge() allocates mappings in
> PMD-sized units, the test may fail with the previous size of 100 MiB,
> which is not a multiple of the PMD size when the base page size is
> 16 KiB or 64 KiB.
>
> 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@xxxxxxxxxx>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>

Thanks for fixing this!

LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>

> ---
>  tools/testing/selftests/mm/guard-regions.c    | 11 ++++++--
>  tools/testing/selftests/mm/ksm_tests.c        | 16 ++++++-----
>  tools/testing/selftests/mm/run_vmtests.sh     |  4 +--
>  tools/testing/selftests/mm/transhuge-stress.c | 25 +++++++++++-------
>  tools/testing/selftests/mm/vm_util.c          | 38 +++++++++++++++++++++++----
>  tools/testing/selftests/mm/vm_util.h          |  9 +++----
>  6 files changed, 72 insertions(+), 31 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
> index b724d62d2b755..eee29ef88cb20 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -2195,14 +2195,21 @@ TEST_F(guard_regions, pagemap_scan)
>  TEST_F(guard_regions, collapse)
>  {
>  	const unsigned long page_size = self->page_size;
> -	const unsigned long size = 2 * HPAGE_SIZE;
> -	const unsigned long num_pages = size / page_size;
> +	const uint64_t hpage_size = pmd_psize();
> +	unsigned long size;
> +	unsigned long num_pages;
>  	char *ptr;
>  	int i;
>
>  	if (!thp_available())
>  		SKIP(return, "Transparent Hugepages not available\n");
>
> +	if (!hpage_size)
> +		ksft_exit_fail_msg("reading hpage_size failed\n");
> +
> +	size = 2 * hpage_size;
> +	num_pages = size / page_size;
> +
>  	/* Need file to be correct size for tests for non-anon. */
>  	if (variant->backing != ANON_BACKED)
>  		ASSERT_EQ(ftruncate(self->fd, size), 0);
> diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
> index 5fd7792a0d479..617e31138af06 100644
> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -521,19 +521,23 @@ static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
>  	struct timespec start_time, end_time;
>  	unsigned long scan_time_ns;
>  	int pagemap_fd, n_normal_pages, n_huge_pages;
> +	const uint64_t hpage_size = pmd_psize();
>
>  	if (!thp_is_enabled()) {
>  		ksft_print_msg("Transparent Hugepages not available\n");
>  		return KSFT_SKIP;
>  	}
>
> +	if (!hpage_size)
> +		ksft_exit_fail_msg("reading hpage_size failed\n");
> +
>  	map_size *= MB;
>  	size_t len = map_size;
>
> -	len -= len % HPAGE_SIZE;
> -	map_ptr_orig = mmap(NULL, len + HPAGE_SIZE, PROT_READ | PROT_WRITE,
> +	len -= len % hpage_size;
> +	map_ptr_orig = mmap(NULL, len + hpage_size, PROT_READ | PROT_WRITE,
>  			MAP_ANONYMOUS | MAP_NORESERVE | MAP_PRIVATE, -1, 0);
> -	map_ptr = map_ptr_orig + HPAGE_SIZE - (uintptr_t)map_ptr_orig % HPAGE_SIZE;
> +	map_ptr = map_ptr_orig + hpage_size - (uintptr_t)map_ptr_orig % hpage_size;
>
>  	if (map_ptr_orig == MAP_FAILED)
>  		err(2, "initial mmap");
> @@ -547,7 +551,7 @@ static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
>
>  	n_normal_pages = 0;
>  	n_huge_pages = 0;
> -	for (void *p = map_ptr; p < map_ptr + len; p += HPAGE_SIZE) {
> +	for (void *p = map_ptr; p < map_ptr + len; p += hpage_size) {
>  		if (allocate_transhuge(p, pagemap_fd) < 0)
>  			n_normal_pages++;
>  		else
> @@ -578,11 +582,11 @@ static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
>  	ksft_print_msg("Average speed:  %.3f MiB/s\n", (map_size / MB) /
>  					       ((double)scan_time_ns / NSEC_PER_SEC));
>
> -	munmap(map_ptr_orig, len + HPAGE_SIZE);
> +	munmap(map_ptr_orig, len + hpage_size);
>  	return KSFT_PASS;
>
>  err_out:
> -	munmap(map_ptr_orig, len + HPAGE_SIZE);
> +	munmap(map_ptr_orig, len + hpage_size);
>  	return KSFT_FAIL;
>  }
>
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index 19755fb4edb94..345d1a79f07ef 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -378,8 +378,8 @@ fi
>  CATEGORY="memfd_secret" run_test ./memfd_secret
>  fi
>
> -# KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100
> -CATEGORY="ksm" run_test ./ksm_tests -H -s 100
> +# KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 512
> +CATEGORY="ksm" run_test ./ksm_tests -H -s 512
>  # KSM KSM_MERGE_TIME test with size of 100
>  CATEGORY="ksm" run_test ./ksm_tests -P -s 100
>  # KSM MADV_MERGEABLE test with 10 identical pages
> diff --git a/tools/testing/selftests/mm/transhuge-stress.c b/tools/testing/selftests/mm/transhuge-stress.c
> index 8eb0c5630e7e3..40ca224a61f49 100644
> --- a/tools/testing/selftests/mm/transhuge-stress.c
> +++ b/tools/testing/selftests/mm/transhuge-stress.c
> @@ -35,12 +35,17 @@ int main(int argc, char **argv)
>  	size_t map_len;
>  	int pagemap_fd;
>  	int duration = 0;
> +	const uint64_t hpage_size = pmd_psize();
> +	const uint64_t hpage_shift = pmd_pshift();
>
>  	ksft_print_header();
>
>  	if (!thp_is_enabled())
>  		ksft_exit_skip("Transparent Hugepages not available\n");
>
> +	if (!hpage_size || !hpage_shift)
> +		ksft_exit_fail_msg("reading hpage_size failed\n");
> +
>  	ram = sysconf(_SC_PHYS_PAGES);
>  	if (ram > SIZE_MAX / psize() / 4)
>  		ram = SIZE_MAX / 4;
> @@ -70,23 +75,23 @@ int main(int argc, char **argv)
>  	}
>
>  	warnx("allocate %zd transhuge pages, using %zd MiB virtual memory"
> -	      " and %zd MiB of ram", len >> HPAGE_SHIFT, len >> 20,
> -	      ram >> (20 + HPAGE_SHIFT - pshift() - 1));
> +	      " and %zd MiB of ram", len >> hpage_shift, len >> 20,
> +	      ram >> (20 + hpage_shift - pshift() - 1));
>
>  	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
>  	if (pagemap_fd < 0)
>  		ksft_exit_fail_msg("open pagemap\n");
>
> -	len -= len % HPAGE_SIZE;
> -	ptr = mmap(NULL, len + HPAGE_SIZE, PROT_RW, mmap_flags, backing_fd, 0);
> +	len -= len % hpage_size;
> +	ptr = mmap(NULL, len + hpage_size, PROT_RW, mmap_flags, backing_fd, 0);
>  	if (ptr == MAP_FAILED)
>  		ksft_exit_fail_msg("initial mmap");
> -	ptr += HPAGE_SIZE - (uintptr_t)ptr % HPAGE_SIZE;
> +	ptr += hpage_size - (uintptr_t)ptr % hpage_size;
>
>  	if (madvise(ptr, len, MADV_HUGEPAGE))
>  		ksft_exit_fail_msg("MADV_HUGEPAGE");
>
> -	map_len = ram >> (HPAGE_SHIFT - 1);
> +	map_len = ram >> (hpage_shift - 1);
>  	map = malloc(map_len);
>  	if (!map)
>  		ksft_exit_fail_msg("map malloc\n");
> @@ -99,7 +104,7 @@ int main(int argc, char **argv)
>  		memset(map, 0, map_len);
>
>  		clock_gettime(CLOCK_MONOTONIC, &a);
> -		for (p = ptr; p < ptr + len; p += HPAGE_SIZE) {
> +		for (p = ptr; p < ptr + len; p += hpage_size) {
>  			int64_t pfn;
>
>  			pfn = allocate_transhuge(p, pagemap_fd);
> @@ -107,7 +112,7 @@ int main(int argc, char **argv)
>  			if (pfn < 0) {
>  				nr_failed++;
>  			} else {
> -				size_t idx = pfn >> (HPAGE_SHIFT - pshift());
> +				size_t idx = pfn >> (hpage_shift - pshift());
>
>  				nr_succeed++;
>  				if (idx >= map_len) {
> @@ -123,7 +128,7 @@ int main(int argc, char **argv)
>  			}
>
>  			/* split transhuge page, keep last page */
> -			if (madvise(p, HPAGE_SIZE - psize(), MADV_DONTNEED))
> +			if (madvise(p, hpage_size - psize(), MADV_DONTNEED))
>  				ksft_exit_fail_msg("MADV_DONTNEED");
>  		}
>  		clock_gettime(CLOCK_MONOTONIC, &b);
> @@ -131,7 +136,7 @@ int main(int argc, char **argv)
>
>  		ksft_print_msg("%.3f s/loop, %.3f ms/page, %10.3f MiB/s\t"
>  			       "%4d succeed, %4d failed, %4d different pages\n",
> -			       s, s * 1000 / (len >> HPAGE_SHIFT), len / s / (1 << 20),
> +			       s, s * 1000 / (len >> hpage_shift), len / s / (1 << 20),
>  			       nr_succeed, nr_failed, nr_pages);
>
>  		if (duration > 0 && b.tv_sec - start.tv_sec >= duration) {
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index e712a980851c8..8f80e73dc22a5 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 __pmd_psize = -1ull;
> +uint64_t __pmd_pshift = -1ull;
>
>  uint64_t pagemap_get_entry(int fd, char *start)
>  {
> @@ -161,19 +163,40 @@ uint64_t pmd_psize(void)
>  	char buf[20];
>  	ssize_t num_read;
>
> +	if (__pmd_psize != -1ull)
> +		return __pmd_psize;
> +
>  	fd = open(PMD_SIZE_FILE_PATH, O_RDONLY);
> -	if (fd == -1)
> +	if (fd == -1) {
> +		__pmd_psize = 0;
>  		return 0;
> +	}
>
>  	num_read = read(fd, buf, 19);
>  	if (num_read < 1) {
> +		__pmd_psize = 0;
>  		close(fd);
>  		return 0;
>  	}
>  	buf[num_read] = '\0';
>  	close(fd);
>
> -	return strtoul(buf, NULL, 10);
> +	__pmd_psize = strtoul(buf, NULL, 10);
> +
> +	return __pmd_psize;
> +}
> +
> +uint64_t pmd_pshift(void)
> +{
> +	if (__pmd_pshift != -1ull)
> +		return __pmd_pshift;
> +
> +	if (__pmd_psize != -1ull)
> +		__pmd_psize = pmd_psize();
> +
> +	__pmd_pshift = (__pmd_psize > 0) ? ffsl(__pmd_psize) - 1 : 0;
> +
> +	return __pmd_pshift;
>  }
>
>  unsigned long rss_anon(void)
> @@ -452,14 +475,19 @@ bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size
>  int64_t allocate_transhuge(void *ptr, int pagemap_fd)
>  {
>  	uint64_t ent[2];
> +	const uint64_t hpage_size = pmd_psize();
> +	const uint64_t hpage_shift = pmd_pshift();
> +
> +	if (!hpage_size || !hpage_shift)
> +		return -1;
>
>  	/* drop pmd */
> -	if (mmap(ptr, HPAGE_SIZE, PROT_READ | PROT_WRITE,
> +	if (mmap(ptr, hpage_size, PROT_READ | PROT_WRITE,
>  		 MAP_FIXED | MAP_ANONYMOUS |
>  		 MAP_NORESERVE | MAP_PRIVATE, -1, 0) != ptr)
>  		ksft_exit_fail_msg("mmap transhuge\n");
>
> -	if (madvise(ptr, HPAGE_SIZE, MADV_HUGEPAGE))
> +	if (madvise(ptr, hpage_size, MADV_HUGEPAGE))
>  		ksft_exit_fail_msg("MADV_HUGEPAGE\n");
>
>  	/* allocate transparent huge page */
> @@ -471,7 +499,7 @@ int64_t allocate_transhuge(void *ptr, int pagemap_fd)
>
>  	if (PAGEMAP_PRESENT(ent[0]) && PAGEMAP_PRESENT(ent[1]) &&
>  	    PAGEMAP_PFN(ent[0]) + 1 == PAGEMAP_PFN(ent[1]) &&
> -	    !(PAGEMAP_PFN(ent[0]) & ((1 << (HPAGE_SHIFT - pshift())) - 1)))
> +	    !(PAGEMAP_PFN(ent[0]) & ((1 << (hpage_shift - pshift())) - 1)))
>  		return PAGEMAP_PFN(ent[0]);
>
>  	return -1;
> diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
> index a40e40c820ef7..71af4804f8f24 100644
> --- a/tools/testing/selftests/mm/vm_util.h
> +++ b/tools/testing/selftests/mm/vm_util.h
> @@ -31,6 +31,8 @@
>
>  extern unsigned int __page_size;
>  extern unsigned int __page_shift;
> +extern uint64_t __pmd_psize;
> +extern uint64_t __pmd_pshift;
>
>  /*
>   * Represents an open fd and PROCMAP_QUERY state for binary (via ioctl)
> @@ -89,6 +91,7 @@ unsigned long pagemap_get_pfn(int fd, char *start);
>  void clear_softdirty(void);
>  bool check_for_pattern(FILE *fp, const char *pattern, char *buf, size_t len);
>  uint64_t pmd_psize(void);
> +uint64_t pmd_pshift(void);
>  unsigned long rss_anon(void);
>  bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
>  bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
> @@ -157,12 +160,6 @@ int ksm_stop(void);
>  int get_hardware_corrupted_size(unsigned long *val);
>  int unpoison_memory(unsigned long pfn);
>
> -/*
> - * On ppc64 this will only work with radix 2M hugepage size
> - */
> -#define HPAGE_SHIFT 21
> -#define HPAGE_SIZE (1 << HPAGE_SHIFT)
> -
>  #define PAGEMAP_PRESENT(ent)	(((ent) & (1ull << 63)) != 0)
>  #define PAGEMAP_PFN(ent)	((ent) & ((1ull << 55) - 1))
>
>
> --
> 2.43.0
>

--
Cheers, Lorenzo