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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 v7 2/3] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260921-fix_split-v7-0-d25ec991159f@arm.com> <20260921-fix_split-v7-2-d25ec991159f@arm.com> <36465f31-59e2-43a5-8cd8-f8bb1844da3c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <36465f31-59e2-43a5-8cd8-f8bb1844da3c@kernel.org> X-Rspam-User: X-Rspamd-Queue-Id: 0EA6720008 X-Stat-Signature: 86x5rcrwkdtiaidx9psiy1wew5fx6kiw X-Rspamd-Server: rspam01 X-HE-Tag: 1790016487-693680 X-HE-Meta: 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 OjCKPk9F mNv1xGgWmrYRTw6+lw10J6E2rdxO6NCF3Z2Zp2o5iSIeZL2fq7z/pnP2vm4bB76kCsfQdXe1gi966amk+Vf3Lam7au2nGJD8nDE7SeVfdjyQIeuhglSbsWLCj1xLXZ9UK57kXVlFAzu6G4/DDRMPJx/g960y+oP8oob6lDg3JfnoZJzPrI9w3Kotf9mDw0sUE25Sz0coUu0WTl+ld8Apm539uDhBJD86sriZmOOF/9Y5H1metWgwYq5nQLE1zxZnBxGO+ZknxlsY8Ha6NiLLiOAlmc/5ziy8LDewpJrMLhWGG4ooKfLltp97t8u+qVTD7XNTHCrsRebPgpDYJpzTM5e1o4isX3Rj+ZcoKL163iJ9Fk6HUhke7vdLSjRsSkqKKYDSTc4962wlQHT6zTewm7xGorZubYYPaqhcR Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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) > > Suggested-by: Zi Yan > > 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? > > > Signed-off-by: Yeoreum Yun > > --- > > tools/testing/selftests/mm/vm_util.c | 137 +++++++++++++++++++++-------------- > > 1 file changed, 84 insertions(+), 53 deletions(-) > > > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > > index 4821a35630363..a7c5caf6925e0 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) > > The function used two tab indent for a reason ;) > > Use two tabs also in the functions you change below. Okay. > > > > > -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); > > No need for () I see. > > > + 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) > > + 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; > > > There is way too much happening here, which makes this rather hard to review. > > Why can't we just focus on the smaps change for now? Yeap. I think we can simplify as your suggestion with a little bit change. I'll spin again. Thanks. > > I.e., something like the following (untested) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index 4821a35630363..5d348d6985026 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -351,24 +351,6 @@ 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) > { > @@ -410,20 +392,34 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages, > return ret; > } > > -bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +static bool __check_pmds(void *start, size_t len, int expected_file_pmds, > + int expected_anon_pmds, uint64_t pmd_pagesize) > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > + int found_anon_pmds = 0, found_file_pmds = 0; > + int pagemap_fd; > + void *addr; > > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_msg("open pagemap fail\n"); > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size); > + for (addr = start; addr < start + len; addr += pmd_pagesize) { > + const uint64_t categories = pagemap_scan_get_categories(pagemap_fd, addr); > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > + if (!(categories & PAGE_IS_HUGE)) > + continue; > + if (categories & PAGE_IS_FILE) > + found_file_pmds++; > + else > + found_anon_pmds++; > + } > + > + close(pagemap_fd); > + return found_anon_pmds == expected_anon_pmds && > + found_file_pmds == expected_file_pmds; > } > > -bool check_huge_file(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(); > > @@ -431,12 +427,12 @@ bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > + return __check_pmds(addr, len, 0, nr_hpages, pmd_pagesize); > > 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) > +bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > { > uint64_t pmd_pagesize = read_pmd_pagesize(); > > @@ -444,11 +440,16 @@ bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); > + return __check_pmds(addr, len, nr_hpages, 0, pmd_pagesize); > > 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_huge_file(addr, len, nr_hpages, hpage_size); > +} > + > int64_t allocate_transhuge(void *ptr, int pagemap_fd) > { > uint64_t ent[2]; > -- > 2.43.0 > -- > Cheers, > > David > -- Sincerely, Yeoreum Yun