On 9/10/26 12:54, Yeoreum Yun wrote: >> On 9/7/26 10:19, Yeoreum Yun wrote: >>> Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on >>> AArch64”), >>> glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations >>> made by memalign(). >>> >>> The underlying VMA may start at a different address from the aligned >>> address returned by memalign(). Furthermore, a subsequent >>> madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is >>> already set. >>> >>> This causes split_huge_page_test to fail because the check_huge_xxx() >>> helpers incorrectly require the address returned by memalign() to >>> match the VMA start address reported in /proc/self/smaps. >>> >>> Instead of relying on /proc/self/smaps, use /proc/self/pagemap and >>> /proc/kpageflags to detect huge-page mappings and large folios: >>> >>> 1. If hpage_size == pmd_pagesize, check PAGE_IS_HUGE instead of >>> using check_large_folios(), since only the mapping type matters. >>> This identifies PMD-mapped huge pages. >>> 2. Otherwise, use check_large_folios() to detect large folios. This >>> covers mTHP cases. >>> 3. Check the folio flags according to the type of huge page. >>> >>> Suggested-by: David Hildenbrand (Arm) <[email protected]> >>> Suggested-by: Zi Yan <[email protected]> >>> Reviewed-by: Zi Yan <[email protected]> >>> Reviewed-by: Baolin Wang <[email protected]> >>> Tested-by: Baolin Wang <[email protected]> >>> Acked-by: Lorenzo Stoakes (ARM) <[email protected]> >>> Signed-off-by: Yeoreum Yun <[email protected]> >>> --- >>> tools/testing/selftests/mm/vm_util.c | 145 >>> ++++++++++++++++++++++------------- >>> tools/testing/selftests/mm/vm_util.h | 1 + >>> 2 files changed, 92 insertions(+), 54 deletions(-) >>> >>> diff --git a/tools/testing/selftests/mm/vm_util.c >>> b/tools/testing/selftests/mm/vm_util.c >>> index 4821a3563036..dc62ce84e143 100644 >> >> [...] >> >>> >>> - if (hpage_size == pmd_pagesize) >>> - return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, >>> hpage_size); >>> +static bool check_huge_type(uint64_t categories, uint64_t kpageflags, >>> + enum check_huge_type type) >>> +{ >>> + const bool file = categories & PAGE_IS_FILE; >>> + const bool swapbacked = kpageflags & KPF_SWAPBACKED; >>> + >>> + switch (type) { >>> + case CHECK_HUGE_ANON: >>> + return !file; >>> + case CHECK_HUGE_FILE: >>> + return file && !swapbacked; >>> + case CHECK_HUGE_SHMEM: >>> + return file & swapbacked; >>> + } >> >> Why do we even need CHECK_HUGE_SHMEM? >> >> That's really just a legacy thing for using smaps to identify huge pages. >> >> It's sufficient to identify CHECK_HUGE_FILE if you know that you have shmem >> mapping. >> >> You will not arbitrarily have non-shmem folios in a shmem mapping :) > > Agree. but there seems the case where discern whethr the mapping is > with regular file or shmem like tmpfs -- khugepaged test where using > __shmem_ops. So I think it would be better to keep this as-is.
Let's not add or maintain unnecessary complexity. hmem_check_huge can really just become check_huge_file. Even file_check_huge can just be simplified. There must be a pretty good reason why we'd want to keep this. -- Cheers, David
