On Tue, Sep 08, 2026 at 12:21:31PM +0200, David Hildenbrand (Arm) wrote: > On 9/8/26 10:23, Yeoreum Yun wrote: > > On Mon, Sep 07, 2026 at 04:36:56PM +0200, David Hildenbrand (Arm) wrote: > >> On 9/7/26 10:15, 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 macros and introduce > >>> pmd_page_shift() > >>> helper to get the HPAGE_SHIFT properly. For HPAGE_SIZE, use pre-existing > >>> helper, read_pmd_pagesize(). > >>> > >>> 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]> > >>> Signed-off-by: Yeoreum Yun <[email protected]> > >>> --- > >> > >> > >> [...] > >> > >>> 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 > >> > >> > >> Why the magic value 512? (desrves a comment) > >> > >> A clear sign that the ksm tests must be rewritten to be standalone and just > >> handle this internally. @Sarthak > > > > Acked. I thought it's enough to spell out in commit message but > > I'll spell out into comment too in this round not refactorying by me > > for ksm test. > > > >> > >>> # 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 > >> > >> [...] > >> > >>> index 4821a3563036..f75bf0bacd18 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_page_size; > >>> +uint64_t __pmd_page_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 (__pmd_page_size) > >>> + return __pmd_page_size; > >>> + > >>> fd = open(PMD_SIZE_FILE_PATH, O_RDONLY); > >>> if (fd == -1) > >>> return 0; > >>> @@ -173,7 +178,25 @@ uint64_t read_pmd_pagesize(void) > >>> buf[num_read] = '\0'; > >>> close(fd); > >>> > >>> - return strtoul(buf, NULL, 10); > >>> + __pmd_page_size = strtoul(buf, NULL, 10); > >>> + > >>> + return __pmd_page_size; > >>> +} > >>> + > >>> +uint64_t pmd_page_shift(void) > >>> +{ > >>> + if (__pmd_page_shift) > >>> + return __pmd_page_shift; > >>> + > >>> + if (!__pmd_page_size) > >>> + __pmd_page_size = read_pmd_pagesize(); > >>> + > >>> + if (!__pmd_page_size) > >>> + return 0; > >>> + > >>> + __pmd_page_shift = (ffsl(__pmd_page_size) - 1); > >>> + > >>> + return __pmd_page_shift; > >>> } > >> The interface is a bit inconsistent. > >> > >> read_pmd_pagesize() vs. pmd_page_shift(). > >> > >> Consider renaming read_pmd_pagesize() to pmd_pagesize() in a cleanup patch. > > > > Okay. > > > >> ... or (better?) adding a size_to_shift() helper instead? > >> > >> I think most places that want the shift also want the size. > >> > >> So this can just be > >> > >> const uint64_t hpage_size = read_pmd_pagesize(); > >> const uint64_t hpage_shift = size_to_shift(hpage_size); > >> > >> > >> In size_to_shift(), you can just handle > >> > >> if (size == 0) > >> return 0; > > > > Hmm, most of tests care mainly two sizes and shiftes -- > > psize()/pshift() and pmd_pagesize() and pmd_pageshift(). > > > > Would it be better to keep both kinda of helpers and > > add size_to_shift() helper for nother hpage size then? > > Works for me as well. As long as it's consistent. > > Maybe even pmd_psize() and pmd_pshift() to match our custom psize() and > pshift()?
Yeap. That would be better. I'll repsin soon. -- Sincerely, Yeoreum Yun
