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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 , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260820-fix_split-v1-0-ab430c58c7cf@arm.com> <20260820-fix_split-v1-2-ab430c58c7cf@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C2DC3A0008 X-Stat-Signature: s66543cs9aj1in9akxeuu7emsiwnsmtx X-HE-Tag: 1787261221-213617 X-HE-Meta: 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 lNSgl3gh nTopGsTt30lFs7Dkm9HzZwJtT8b9M1hCMMMQ1KYlu5tQkw3evuLyFsAeJnFPCVB904u3ZtGrEmhfu1KRar2Juj0158jzCRtDHu+3V3/zlGLjde2b3szYFEi0PpR2I66ubD5mg2/mcqFMZ8j5a46+JgDT/AVg+kcH4/8WjgBQiUoWzxZseeX38TagA3Ul3PQxWbefoBz3LzEF4z8I+BL/jvA4jIYHXc7uB+u+Z9HLA3UNesLVLsG7AL7pRadMqjLr4Ol3YwVr0JvbsZtBTjcPKjq7cizPDxJRj9fhsYgz3d9ueo2yzU/HUfNwBt2Jun4NB5yODDGYux1Sp7OfJReoMXKta8a2yhMTy52isA5FdEOcRCKOu6vBQz/zUCzcE5uShlSVbJ+anLVHeV+u8KqbYWZbY+8nwablhHZKt Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Thu Aug 20, 2026 at 3:40 PM EDT, 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. > > > > Fix this by using /proc/self/pagemap and /proc/kpageflags instead of > > /proc/self/smaps to detect huge pages and change the meaning of > > check_huge_xxx()'s nr_hpages argument: > > Have you checked Baolin's patches[1] in mm-new? They resue > gather_after_split_folio_orders() to reimplement check_huge_xxx(), also > based on pagemap and kpageflags. Does it fix the issue? > > [1] https://lore.kernel.org/all/cover.1785985999.git.baolin.wang@linux.alibaba.com/ > Unfortunately, No. since __check_pmd_huge() in check_huge_xxx() still use /proc/self/smaps [1] for pmd THP, it still has problem though ths patch series applied. [1] https://lore.kernel.org/all/56b16691f605426b33b5cf47319233de6127a6b3.1785985999.git.baolin.wang@linux.alibaba.com/ > > > > - nr_hpages > 0: check all of pages in the range are huge page. > > - nr_hpages < 0: check all of pages in the range are not huge page. > > - nr_hpages == 0: invalid. > > > > Reported-by: David Hildenbrand (Arm) > > Signed-off-by: Yeoreum Yun > > --- > > tools/testing/selftests/mm/khugepaged.c | 26 ++--- > > tools/testing/selftests/mm/split_huge_page_test.c | 6 +- > > tools/testing/selftests/mm/vm_util.c | 135 ++++++++++++++++++---- > > tools/testing/selftests/mm/vm_util.h | 1 + > > 4 files changed, 131 insertions(+), 37 deletions(-) > > > > > -- > Best Regards, > Yan, Zi > -- Sincerely, Yeoreum Yun