On 9/21/26 20:48, Yeoreum Yun wrote: > Hi, > >> On 9/21/26 12:40, 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. >>> >>> Since shmem pages are also file-backed, simply check whether the page >>> is file-backed. >>> >>> Suggested-by: David Hildenbrand (Arm) <[email protected]> >>> Suggested-by: Zi Yan <[email protected]> >> >> Do we need a Fixes: tag? > > Since this change is required for the chaning of behavior of glibc, > I don't think we don't need to add Fixes tag in here? > Our test made wrong assumptions on the underlying behavior of the user space allocator (no VMA merging would happen). So I'd argue that we should add a Fixes: for the test.
-- Cheers, David
