From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 027FA4BFE9D; Thu, 10 Sep 2026 10:54:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789037669; cv=none; b=Z4ePC3Ls5bOI67A7D0ZBF3f4yqZVao/h4axcYsnuY0XA+EXSCXMmOG3h5zPVhPb9jndBxGhBKecRy2tUAPF50Kti50TgkVQ/voLshEG5UIR3ttr9Hz2L12KdGeYLO++QuY4jyapKjMc9v8XVxxpAtYtftejDaoG57+yrhKdiyGY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789037669; c=relaxed/simple; bh=LZa/mTe3VR25KHQaR9yMTJp7T+IkVsTbaUvpTI1sUo8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BDLMJh5r+45DcomNJxHJNI20PeCcNj2Y9//gNCo8tvAc+qbKsIfmezokqmxuN7mn6o14C2vPkGMk9DdJ+pjtwGDv1MzckVho1z4ToVmXv8WbIFwCnxlmHNC0XLBmcihtRWczSFr5ODVLYlhAmexBqN7U6RDSKm7CuLfmCaDHAlA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=VN6MoQBj; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="VN6MoQBj" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DE2211477; Thu, 10 Sep 2026 03:54:15 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 19E8E3F7B4; Thu, 10 Sep 2026 03:54:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789037659; bh=LZa/mTe3VR25KHQaR9yMTJp7T+IkVsTbaUvpTI1sUo8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VN6MoQBjtpr1/cmo6G/4YZh5bHXuew9SIhpd11l+692psl/N9na3NbHc21NOsAUsU 3+TQmValjDyMFstToPCzXuQUZ63eChLMNCBjyW+gx19SIlNi9MqfNzNAp+KP3fHIbQ 6G3FQnvZE1lwfmo6X/7iJEX6alz2jYz4JAF7kQnc= Date: Thu, 10 Sep 2026 11:54:13 +0100 From: Yeoreum Yun To: "David Hildenbrand (Arm)" Cc: Yeoreum Yun , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. 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 v5 2/3] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260907-fix_split-v5-0-822b810458bc@arm.com> <20260907-fix_split-v5-2-822b810458bc@arm.com> <956df69d-8c0a-420f-889e-7df2842605dc@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <956df69d-8c0a-420f-889e-7df2842605dc@kernel.org> > 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) > > Suggested-by: Zi Yan > > Reviewed-by: Zi Yan > > Reviewed-by: Baolin Wang > > Tested-by: Baolin Wang > > Acked-by: Lorenzo Stoakes (ARM) > > Signed-off-by: Yeoreum Yun > > --- > > 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. > > > > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > > + return false; > > } > > > > -bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > > +static bool __check_huge(void *addr, size_t len, int nr_hpages, > > + uint64_t hpage_size, enum check_huge_type type) > > { > > - uint64_t pmd_pagesize = read_pmd_pagesize(); > > + bool ret = false; > > + int pagemap_fd, kpageflags_fd; > > + int nr_pmd_mappings = 0; > > + uint64_t pmd_pagesize, scan_mapping_size; > > + uint64_t categories, kpf; > > + unsigned long pfn; > > + bool check_pmd_mapping, allow_nonpresent; > > + char *start = addr; > > + char *end = start + len; > > > > + pmd_pagesize = read_pmd_pagesize(); > > if (!pmd_pagesize) > > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > > > - if (hpage_size == pmd_pagesize) > > - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > > + check_pmd_mapping = (hpage_size == pmd_pagesize); > > + scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize(); > > + /* Some mTHP tests check a partially populated PMD-sized range. */ > > + allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len; > > > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > > + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > > + if (pagemap_fd < 0) > > + ksft_exit_fail_msg("open pagemap fail\n"); > > + > > + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > > + if (kpageflags_fd < 0) { > > + close(pagemap_fd); > > No need to cleanup when exiting. Yes, but some test code does clean it up, so I was just confused about the convention :\ > > > + ksft_exit_fail_msg("open kpageflags fail\n"); > > + } > > + > > + if (!check_pmd_mapping && > > + !check_large_folios(pagemap_fd, kpageflags_fd, > > + addr, len, nr_hpages, hpage_size)) > > + goto out; > > + > > + for (; start < end; start += scan_mapping_size) { > > + categories = pagemap_scan_get_categories(pagemap_fd, start); > > + pfn = pagemap_get_pfn(pagemap_fd, start); > > + if (pfn == -1UL) { > > + if (!allow_nonpresent) > > + goto out; > > + else > > + continue; > > + } > > + if (pageflags_get(pfn, kpageflags_fd, &kpf)) > > + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno)); > > + if (check_pmd_mapping && (categories & PAGE_IS_HUGE)) > > + nr_pmd_mappings++; > > + if (kpf & KPF_COMPOUND_TAIL) > > + continue; > > + if (!check_huge_type(categories, kpf, type)) > > + goto out; > > + } > > + > > + if (check_pmd_mapping && (nr_pmd_mappings != nr_hpages)) > > + goto out; > > + ret = true; > > + > > +out: > > + close(pagemap_fd); > > + close(kpageflags_fd); > > + return ret; > > } > > > > -- > Cheers, > > David > -- Sincerely, Yeoreum Yun