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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 v2 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260826-fix_split-v2-0-71153c7f579a@arm.com> <20260826-fix_split-v2-2-71153c7f579a@arm.com> <0107447a-7c1f-44f8-94fb-109b0f850677@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0107447a-7c1f-44f8-94fb-109b0f850677@linux.alibaba.com> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 120B540005 X-Stat-Signature: ngbpa9rzadoanm9k7rmwcpp9oawcoxrm X-HE-Tag: 1787827464-878228 X-HE-Meta: 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 sIxiaYcR GrunHIbV+Tzs9kf1QSulgyZtY/f1djuHP+XOf/VrPkHDGoG9Rx8LxdV2vjr99WXxABZ/ifJ0F47J4ch30iKyWsi5MVPVvEbTsOQyFpiRd3xlA24UWXUzWFkjyTP+qLoRVRAafvXq/Ic+5pHd+UpEGla8txpfrYh1dV2hhLm2NW3DmBJgR/SzhwF0hh9t6Wq4s9aTlfvkbEG+hWIJdMPe6y2BPB9u4jYgy84hfrCS5AnLUlbz4knEvPdKJXJeMfgRw+P2Ti/VqrCG9rHWacOfHlIqolAmRoFEloezwQcm9Ugj8VFSP8SZ1gblnALZqBS/uduY7Ud0Fm8K+h0P0qdBWw+enaJ70KxjvYYHH2KEgma8tshlhRK2nzfDzHJfzJCZC44eS6MQikba664I= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Baolin, > > > 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. But, It seems to valuable to check other page-flags than checking the large-folio only. > > > { > > - 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. Since for a split case, large folio can be as-is but only remove the PMD mapping only, skipping the large_folio checking seems valid when nr_hpage is 0. And the failure of test seems because of unmapped area after changinng the collapse-order. Therefore, it seems to fine with below patch: ---------------&<---------------------- diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index 1d0959b3b9e8..f174a76d2310 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -387,14 +387,14 @@ enum check_huge_type { 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) +static bool __check_huge(void *addr, size_t len, int nr_hpages, + uint64_t hpage_size, enum check_huge_type type) { int pagemap_fd, kpageflags_fd; uint64_t pmd_pagesize, granule; uint64_t categories, kpf; unsigned long pfn; - bool check_large, huge_mapped; + bool check_large, check_huge_mapped, allow_nomap; char *start = addr; char *end = start + len; @@ -405,11 +405,20 @@ static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages, if (nr_hpages > 0) { check_large = true; granule = hpage_size; + if (granule == pmd_pagesize) + check_huge_mapped = true; + else + check_huge_mapped = false; } else { check_large = false; granule = psize(); } + if (nr_hpages * hpage_size < len) + allow_nomap = true; + else + allow_nomap = false; + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); if (pagemap_fd < 0) ksft_exit_fail_msg("open pagemap fail\n"); @@ -428,18 +437,15 @@ static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages, categories = pagemap_scan_get_categories(pagemap_fd, start); pfn = pagemap_get_pfn(pagemap_fd, start); if (pfn == -1UL) { - if (check_large) + if (!allow_nomap) 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) + if (check_huge_mapped != !!(categories & PAGE_IS_HUGE)) goto out; - } if (kpf & KPF_COMPOUND_TAIL) continue; if (!!(categories & PAGE_IS_FILE) != (type != CHECK_HUGE_ANON)) @@ -458,17 +464,17 @@ static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages, bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) { - return __check_pmd_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON); + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON); } 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_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE); } 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); + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_SHMEM); } If it's good for you, I'll repost again. Thanks! -- Sincerely, Yeoreum Yun