From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
akpm@linux-foundation.org, david@kernel.org, liam@infradead.org,
vbabka@kernel.org, rppt@kernel.org, surenb@google.com,
mhocko@suse.com, shuah@kernel.org, ziy@nvidia.com,
baolin.wang@linux.alibaba.com, nico.pache@linux.dev,
ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org,
lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org
Subject: Re: [PATCH] kselftest: mm: remove HPAGE_SIZE and HPAGE_SHIFT macro
Date: Thu, 3 Sep 2026 09:56:40 +0100 [thread overview]
Message-ID: <apk1WVEDYtQhRxWR@gremlin> (raw)
In-Reply-To: <20260902175611.1241118-1-yeoreum.yun@arm.com>
On Wed, Sep 02, 2026 at 06:56:11PM +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 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
> 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.
Probably worth spelling out Least Common Denominator for those who might
mistaken this for a kind of display panel :P
I also wonder if it's worth pulling that out as a separate patch in a series for
better bisectability?
>
> 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>
Firstly THANK YOU for doing this :) hugely appreciated.
Also thank you again for the birthday cakes ;)
And apologies for the nitpicks :P
> ---
> tools/testing/selftests/mm/guard-regions.c | 12 +++++--
> tools/testing/selftests/mm/ksm_tests.c | 17 ++++++----
> tools/testing/selftests/mm/run_vmtests.sh | 4 +--
> tools/testing/selftests/mm/transhuge-stress.c | 22 +++++++------
> tools/testing/selftests/mm/vm_util.c | 32 ++++++++++++++++---
> tools/testing/selftests/mm/vm_util.h | 9 ++----
> 6 files changed, 66 insertions(+), 30 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
> index 5c8ec3ca75d7..d370592b291f 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -2195,14 +2195,22 @@ 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;
> + uint64_t hpage_size;
> + unsigned long size;
> + unsigned long num_pages;
> char *ptr;
> int i;
>
> if (!thp_available())
> SKIP(return, "Transparent Hugepages not available\n");
>
> + hpage_size = read_pmd_pagesize();
> + 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 5fd7792a0d47..278e77055007 100644
> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -521,6 +521,11 @@ 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;
> + uint64_t hpage_size = read_pmd_pagesize();
NIT: can this be const?
> +
> + if (!hpage_size) {
> + ksft_exit_fail_msg("reading hpage_size failed\n");
> + }
NIT: can drop the {}
>
> if (!thp_is_enabled()) {
> ksft_print_msg("Transparent Hugepages not available\n");
> @@ -530,10 +535,10 @@ static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
> 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 +552,7 @@ 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 +583,11 @@ 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 d09f9f6a384e..24aa1de27c25 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -360,8 +360,8 @@ 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
See above re: splitting out.
> # 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 8eb0c5630e7e..66ae94afaf8d 100644
> --- a/tools/testing/selftests/mm/transhuge-stress.c
> +++ b/tools/testing/selftests/mm/transhuge-stress.c
> @@ -35,6 +35,8 @@ int main(int argc, char **argv)
> size_t map_len;
> int pagemap_fd;
> int duration = 0;
> + uint64_t hpage_size = read_pmd_pagesize();
> + uint64_t hpage_shift = hpshift();
NIT: could be consts?
>
> ksft_print_header();
>
> @@ -70,23 +72,23 @@ 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 +101,7 @@ 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 +109,7 @@ 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 +125,7 @@ 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 +133,7 @@ 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 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;
>
> uint64_t pagemap_get_entry(int fd, char *start)
> {
> @@ -161,6 +163,9 @@ uint64_t read_pmd_pagesize(void)
> char buf[20];
> ssize_t num_read;
>
> + if (__hpage_size)
> + return __hpage_size;
> +
> fd = open(PMD_SIZE_FILE_PATH, O_RDONLY);
> if (fd == -1)
> return 0;
> @@ -173,7 +178,24 @@ uint64_t read_pmd_pagesize(void)
> buf[num_read] = '\0';
> close(fd);
>
> - return strtoul(buf, NULL, 10);
> + __hpage_size = strtoul(buf, NULL, 10);
> +
> + return __hpage_size;
> +}
> +
> +uint64_t hpshift(void)
> +{
> + if (!__hpage_shift) {
> + if (!__hpage_size) {
> + __hpage_size = read_pmd_pagesize();
> + if (!__hpage_size)
> + ksft_exit_fail_msg("reading __hpage_size failed\n");
> + }
This nesting is a bit horrifying :P
Maybe:
if (__hpage_shift && __hpage_size)
return;
if (!__hpage_size) {
...
}
if (!__hpage_shift) {
...
}
?
> +
> + __hpage_shift = (ffsl(__hpage_size) - 1);
> + }
> +
> + return __hpage_shift;
> }
>
> unsigned long rss_anon(void)
> @@ -452,14 +474,16 @@ 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];
> + uint64_t hpage_size = read_pmd_pagesize();
> + uint64_t hpage_shift = hpshift();
NIT: could be const?
>
> /* 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 +495,7 @@ 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 9a49af88702e..20a6334605c7 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 __hpage_size;
> +extern uint64_t __hpage_shift;
>
> /*
> * 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 read_pmd_pagesize(void);
> +uint64_t hpshift(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)
> -
Worth calling this change out in commit msg also?
> #define PAGEMAP_PRESENT(ent) (((ent) & (1ull << 63)) != 0)
> #define PAGEMAP_PFN(ent) ((ent) & ((1ull << 55) - 1))
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>
--
Cheers, Lorenzo
next prev parent reply other threads:[~2026-09-03 8:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-02 17:56 [PATCH] kselftest: mm: remove HPAGE_SIZE and HPAGE_SHIFT macro Yeoreum Yun
2026-09-02 19:29 ` Andrew Morton
2026-09-03 8:51 ` Yeoreum Yun
2026-09-03 8:56 ` Lorenzo Stoakes (ARM) [this message]
2026-09-03 11:39 ` Yeoreum Yun
2026-09-03 14:46 ` Yeoreum Yun
2026-09-03 14:47 ` Lorenzo Stoakes (ARM)
2026-09-03 11:12 ` Sarthak Sharma
2026-09-03 11:40 ` Yeoreum Yun
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