Hi Yeoreum!
On 10/13/26 3:16 PM, 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) <[email protected]>
> Tested-by: Sarthak Sharma <[email protected]>
> Reviewed-by: Zi Yan <[email protected]>
> Reviewed-by: Sarthak Sharma <[email protected]>
> Signed-off-by: Yeoreum Yun <[email protected]>
> ---
[...]
> diff --git a/tools/testing/selftests/mm/vm_util.c
> b/tools/testing/selftests/mm/vm_util.c
> index 5f2fb5b819c4a..efd99298be135 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();
Kiryl pointed this out in v5 [1], you might have missed it. This check
seems to be inverted.
[1] https://lore.kernel.org/all/asj4dT2Q__SlKhgr@thinkstation/
