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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3502; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=JS+WBqmWmrP2fdC1UeFFZUubf/2Ll0DO5dqgbi/DZMw=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqnnOR4knPYbXph4THLv5aahxcy3nFmOr67YDBu Ikk6BgXFYuJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCap5zkQAKCRBt1cPRWsUx MxwFC/94h60W5/bgOuiN6T1eWWPcRTmyR8sgt8i3utKJkv9p33t4rzj812FPIhmNEK3/U6AQ84b Yuu3t3jsbi+gkNg5Cq+teedoStA9FFwluk5xsCULbr9p/wbyU2WLLTumdYRPtOYSOzBRIcV4wBW O8UqZ0qTBagHJ8zIkLkJOLhsejbNw5/GCIJ32g7Rwzm73GQYcMnfpFPmmV35VUok/VBQm9PhuKa YBrOU+ulrwhzBHTUPlCWH6p0x/lDXKyA0f9sAH5DL/NQBxpBxquD5NV45F0fdG/10c9W3DVP4ql 8b/LMfBjJJvmjm4SzuADBuwq/yGC6SE0k2WSJEoEWMGjzSEFUnbRF2ZmYeMsF20kwoDFJ1Q9cgm sEyJIJUdpIPVCGkE08iSYZtcbkv48/RrJiJGU7YhRQ9sBfBZ2kTRsSRctDz0/7AXd8+Nrbw1sID GsDkOFDnjj7GXtIt2jKAL6xiQwCU3zd15e2p4cMHTSVX8F6JYr8kyrqWJHiCa27pta5YU= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 X-Stat-Signature: g4ruua6kss83rtdx5ck3kawwfnd4fbct X-Rspamd-Queue-Id: F07B940002 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788769174-43483 X-HE-Meta: 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 +gQqB8X7 Bf6Y/8TdU2eHwA+CXIy/3wKmDfpi1/5bBU9B8iNbFuCqkFaxKUFA/d9HSlBvXrbcCgfRIfluU1DFC1DqNtemQb1Io0Ps0MUiIj7G5dOnwXGv0K2dtNM08vWS4oEKMC4r0m7au1s2Hh1Tm42E8U+KwrUHajgXx9qDkcQzvZe/hRlW0tp2R3L1ZTmIVpJaeWpLsSM/CNwgHvrCx/+XWOKNLsMzYBHqfHQjFVrJzHtao/W/yqLMWbcLtC6zpUibZ97MdrKCypwByfbTG+X9tAroe6gcgQ0tPkFZq6af093oKH68DvOtdVN0J17u5RvISsPQriT2UE4pnrlK7+n3T3M/Zxz+BBZC7o3pW2W2e Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: split_huge_page_test can fail for the following reasons: 1. During the test, khugepaged may collapse previously split pages again, causing intermittent failures. 2. 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(). Moreover, a subsequent madvise(MADV_HUGEPAGE) call does not split the VMA because it already has the same advice. This causes the 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. Address these issues by applying MADV_NOHUGEPAGE after faulting in the huge page, preventing khugepaged from collapsing it again, and 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. Also, current usage of memalign() would result memory area may unexpectedly merge with an adjacent VMA, causing tests that inspect it through /proc/self/smaps to fail. Eliminate this potential source of test flakiness by introducing alloc_isolated_mem(), which places guard regions before and after the allocated area to prevent unexpected VMA merging. This patch based on mm-unstable --- Changes in v5: - rename madv_nohuge() to disable_khugepaged(). - Link to v4: https://lore.kernel.org/r/20260902-fix_split-v4-0-85f03905f7b1@arm.com Changes in v4: - reparse commit message. - introduce alloc_isolated_mem(). - make madv_nohuge() helper according to suggestion. - Link to v3: https://lore.kernel.org/r/20260828-fix_split-v3-0-374022586a4b@arm.com Changes in v3: - change message in case of failure of madvise() with MADV_NOHUGEPAGE. - fix collapse_single_mthp (mthp_khugepaged:anon) test case failure. - Link to v2: https://lore.kernel.org/all/20260826-fix_split-v2-0-71153c7f579a@arm.com/ Changes in v2: - rebase to mm-unstable. - add message in case of failure of madvise() with MADV_NOHUGEPAGE. - fix wrong setup expected_huge in check_huge_shmem(). - Link to v1: https://lore.kernel.org/r/20260820-fix_split-v1-0-ab430c58c7cf@arm.com --- Yeoreum Yun (3): kselftest: mm: prevent random failure of huge page split for khugepaged kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper kselftest: mm: introduce alloc_isolated_mem() tools/testing/selftests/mm/pagemap_ioctl.c | 18 +- tools/testing/selftests/mm/soft-dirty.c | 6 +- tools/testing/selftests/mm/split_huge_page_test.c | 27 ++- tools/testing/selftests/mm/vm_util.c | 212 ++++++++++++++++------ tools/testing/selftests/mm/vm_util.h | 3 + 5 files changed, 192 insertions(+), 74 deletions(-) --- base-commit: d118502628f8b673be9023db8bdf878f64a7ed45 change-id: 20260820-fix_split-f44939ec44b8 Best regards, -- Sincerely, Yeoreum Yun