From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E58483CF1F0; Thu, 27 Aug 2026 08:28:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.113 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787819301; cv=none; b=qdWwouHbfOktFQLcNAI4whKZKLIhWrPFT3YtN46/YlWyg3YkNjX5Gs87sEvx0Ey2l8CLYN8XMb2zW4DKlzJSnD4Ztybx+L3ez0t/NOeHZjGKqyh7F0HtnIjpziv8T8YSjxK3ITLmGZfkA58TaM9yQ3NvFIpEkLHjkfaqvS8o0tU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787819301; c=relaxed/simple; bh=giqeAkD1Vc9WT3IBTjcmjVEXQSQpBSGwdcKcXvjnzRw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IpLLh+3Hqeblyt/sNHc8GsR/MLjjT2uVSfM3TP9M6jyxWQzX/YOMKbBZ/JxKDeByESWq/nLb8gPfeg37Dg3D+OmpjD0oipn9j5wiWoGYno+s5VCDZoohGya066xA/07QTam1f4iTbaUe8wcKblIwSkTTnxOdZak5DShUA+Ngai0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=PgzkalWw; arc=none smtp.client-ip=115.124.30.113 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="PgzkalWw" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1787819285; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=7ZyKXiDcMnJRL/Jca9p3GNNTfZ89CGVivxP5tkkYlU4=; b=PgzkalWwZQeBO1KJOXcWmv3mKarhsMZgdBEoih7LZcF4TPs6BkQhuhkHCnkao1/Eo63u1plO4nsSS1dO49gfvIj3e7il0mJkWLMzxUmJfTBfpUbcb4hEb5zqndT2xaCU44MghwRWjAAVRUt1j3xv6xZkaVK2i7Bxzx4ZfKNFfW8= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R881e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=21;SR=0;TI=SMTPD_---0X9j9eTi_1787819282; Received: from 30.74.144.120(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X9j9eTi_1787819282 cluster:ay36) by smtp.aliyun-inc.com; Thu, 27 Aug 2026 16:28:03 +0800 Message-ID: <0107447a-7c1f-44f8-94fb-109b0f850677@linux.alibaba.com> Date: Thu, 27 Aug 2026 16:28:01 +0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper To: Yeoreum Yun , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , "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 Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260826-fix_split-v2-0-71153c7f579a@arm.com> <20260826-fix_split-v2-2-71153c7f579a@arm.com> From: Baolin Wang In-Reply-To: <20260826-fix_split-v2-2-71153c7f579a@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/26/26 8:24 PM, 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. > > Reported-by: David Hildenbrand (Arm) > Signed-off-by: Yeoreum Yun > --- > tools/testing/selftests/mm/vm_util.c | 130 ++++++++++++++++++++--------------- > tools/testing/selftests/mm/vm_util.h | 1 + > 2 files changed, 77 insertions(+), 54 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index 4821a3563036..1d0959b3b9e8 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -351,31 +351,13 @@ char *__get_smap_entry(void *addr, const char *pattern, char *buf, size_t len) > return entry; > } > > -static bool __check_pmd_huge(void *addr, char *pattern, int nr_hpages, > - uint64_t hpage_size) > -{ > - char buffer[MAX_LINE_LENGTH]; > - uint64_t thp = -1; > - char *entry; > - > - entry = __get_smap_entry(addr, pattern, buffer, sizeof(buffer)); > - if (!entry) > - goto err_out; > - > - if (sscanf(entry, "%9" SCNu64 " kB", &thp) != 1) > - ksft_exit_fail_msg("Reading smap error\n"); > - > -err_out: > - return thp == (nr_hpages * (hpage_size >> 10)); > -} > - > -static bool check_large_folios(void *addr, size_t len, int nr_hpages, > - uint64_t hpage_size) > +static bool check_large_folios(int pagemap_fd, int kpageflags_fd, > + void *addr, size_t len, int nr_hpages, > + uint64_t hpage_size) > { > int order = 0, pagesize = getpagesize(); > unsigned int nr_pages = hpage_size / pagesize; > int orders[MAX_NR_ORDERS], status; > - int pagemap_fd, kpageflags_fd; > bool ret = false; > > if (!nr_pages) > @@ -386,15 +368,6 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages, > ksft_exit_fail_msg("invalid order\n"); > > memset(orders, 0, sizeof(int) * MAX_NR_ORDERS); > - pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > - if (pagemap_fd == -1) > - ksft_exit_fail_msg("read pagemap fail\n"); > - > - kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > - if (kpageflags_fd == -1) { > - close(pagemap_fd); > - ksft_exit_fail_msg("read kpageflags fail\n"); > - } > > status = gather_folio_orders(addr, len, pagemap_fd, > kpageflags_fd, orders, MAX_NR_ORDERS); > @@ -405,48 +378,97 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages, > ret = true; > > out: > - close(pagemap_fd); > - close(kpageflags_fd); > return ret; > } > > -bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +enum check_huge_type { > + CHECK_HUGE_ANON, > + CHECK_HUGE_FILE, > + CHECK_HUGE_SHMEM, > +}; > + > +static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages, > + uint64_t hpage_size, enum check_huge_type type) The original __check_pmd_huge() is only for PMD-sized large folios, but now it not only checks PMD-sized large folios but also mTHP large folios, which I find confusing. Please keep its original semantics, and only check PMD-sized large folios. > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > + int pagemap_fd, kpageflags_fd; > + uint64_t pmd_pagesize, granule; > + uint64_t categories, kpf; > + unsigned long pfn; > + bool check_large, huge_mapped; > + 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, "AnonHugePages: ", nr_hpages, hpage_size); > + if (nr_hpages > 0) { > + check_large = true; > + granule = hpage_size; > + } else { > + check_large = false; > + granule = psize(); > + } This is incorrect for the mTHP large folio check. I already hit a selftest failure. Please test your patches before sending them out. [root@]./khugepaged -c 4 mthp_khugepaged:anon TAP version 13 # Save THP and khugepaged settings... OK 1..4 # Allocate huge page on fault... OK # Split huge PMD on MADV_DONTNEED... OK ok 1 allocate on fault and split # # Run test: collapse_full (mthp_khugepaged:anon) # Collapse multiple fully populated PTE table.... OK ok 2 collapse_full # # Run test: collapse_empty (mthp_khugepaged:anon) # Do not collapse empty PTE table.... OK ok 3 collapse_empty # # Run test: collapse_single_mthp (mthp_khugepaged:anon) # Collapse PTE table with half PTE entries present.... Fail not ok 4 collapse_single_mthp # Totals: pass:3 fail:1 xfail:0 xpass:0 skip:0 error:0 > - 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"); > > -bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > -{ > - uint64_t pmd_pagesize = read_pmd_pagesize(); > + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > + if (kpageflags_fd < 0) { > + close(pagemap_fd); > + ksft_exit_fail_msg("open kpageflags fail\n"); > + } > > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > + if (check_large && !check_large_folios(pagemap_fd, kpageflags_fd, > + addr, len, nr_hpages, hpage_size)) > + goto out; > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > + for (; start < end; start += granule) { > + categories = pagemap_scan_get_categories(pagemap_fd, start); > + pfn = pagemap_get_pfn(pagemap_fd, start); > + if (pfn == -1UL) { > + if (check_large) > + goto out; > + else > + continue; > + } > + if (pageflags_get(pfn, kpageflags_fd, &kpf)) > + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno)); > + huge_mapped = categories & PAGE_IS_HUGE; > + if (check_large != huge_mapped) { > + if (!check_large || granule == pmd_pagesize) > + goto out; > + } > + if (kpf & KPF_COMPOUND_TAIL) > + continue; > + if (!!(categories & PAGE_IS_FILE) != (type != CHECK_HUGE_ANON)) > + goto out; > + if (type == CHECK_HUGE_ANON) > + continue; > + if (!!(kpf & KPF_SWAPBACKED) != (type != CHECK_HUGE_FILE)) > + goto out; > + } > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > +out: > + close(pagemap_fd); > + close(kpageflags_fd); > + return start >= end; > } > > -bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > - > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > + return __check_pmd_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON); > +} > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); > +bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +{ > + return __check_pmd_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE); > +} > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > +bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +{ > + return __check_pmd_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_SHMEM); > } > > int64_t allocate_transhuge(void *ptr, int pagemap_fd) > diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h > index 9a49af88702e..f19bd17817e5 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -18,6 +18,7 @@ > #define PM_SWAP BIT_ULL(62) > #define PM_PRESENT BIT_ULL(63) > > +#define KPF_SWAPBACKED BIT_ULL(14) > #define KPF_COMPOUND_HEAD BIT_ULL(15) > #define KPF_COMPOUND_TAIL BIT_ULL(16) > #define KPF_HWPOISON BIT_ULL(19) >