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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 3/4] selftests/mm: reimplement is_backed_by_thp() with more precise check Message-ID: <20250813214112.tarr5rbamtc6cmie@master> Reply-To: Wei Yang References: <20250812155512.926011-1-ziy@nvidia.com> <20250812155512.926011-4-ziy@nvidia.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250812155512.926011-4-ziy@nvidia.com> User-Agent: NeoMutt/20170113 (1.7.2) On Tue, Aug 12, 2025 at 11:55:11AM -0400, Zi Yan wrote: >and rename it to is_backed_by_folio(). > >is_backed_by_folio() checks if the given vaddr is backed a folio with >a given order. It does so by: >1. getting the pfn of the vaddr; >2. checking kpageflags of the pfn; > >if order is greater than 0: >3. checking kpageflags of the head pfn; >4. checking kpageflags of all tail pfns. > >pmd_order is added to split_huge_page_test.c and replaces max_order. > >Signed-off-by: Zi Yan >--- > .../selftests/mm/split_huge_page_test.c | 67 +++++++++++++------ > tools/testing/selftests/mm/vm_util.c | 2 +- > tools/testing/selftests/mm/vm_util.h | 1 + > 3 files changed, 48 insertions(+), 22 deletions(-) > >diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c >index 63ac82f0b9e0..3aaf783f339f 100644 >--- a/tools/testing/selftests/mm/split_huge_page_test.c >+++ b/tools/testing/selftests/mm/split_huge_page_test.c >@@ -25,6 +25,7 @@ > uint64_t pagesize; > unsigned int pageshift; > uint64_t pmd_pagesize; >+unsigned int pmd_order; > > #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages" > #define SMAP_PATH "/proc/self/smaps" >@@ -36,23 +37,48 @@ uint64_t pmd_pagesize; > > #define GET_ORDER(nr_pages) (31 - __builtin_clz(nr_pages)) > >-int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file) >+int is_backed_by_folio(char *vaddr, int order, int pagemap_fd, int kpageflags_fd) > { >- uint64_t paddr; >- uint64_t page_flags; >+ unsigned long pfn_head; >+ uint64_t pfn_flags; >+ unsigned long pfn; >+ unsigned long i; > >- if (pagemap_file) { >- pread(pagemap_file, &paddr, sizeof(paddr), >- ((long)vaddr >> pageshift) * sizeof(paddr)); >+ if (!pagemap_fd || !kpageflags_fd) >+ return 0; The same in patch 2. > >- if (kpageflags_file) { >- pread(kpageflags_file, &page_flags, sizeof(page_flags), >- PAGEMAP_PFN(paddr) * sizeof(page_flags)); >+ pfn = pagemap_get_pfn(pagemap_fd, vaddr); > >- return !!(page_flags & KPF_THP); >- } >+ if (pfn == -1UL) >+ return 0; >+ >+ if (get_pfn_flags(pfn, kpageflags_fd, &pfn_flags)) >+ return 0; >+ >+ if (!order) { >+ if (pfn_flags & (KPF_THP | KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL)) >+ return 0; >+ return 1; > } >- return 0; >+ >+ if (!(pfn_flags & KPF_THP)) >+ return 0; >+ >+ pfn_head = pfn & ~((1 << order) - 1); >+ >+ if (get_pfn_flags(pfn_head, kpageflags_fd, &pfn_flags)) >+ return 0; >+ >+ if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_HEAD))) >+ return 0; >+ >+ for (i = 1; i < (1UL << order) - 1; i++) { Do we miss the last tail? >+ if (get_pfn_flags(pfn_head + i, kpageflags_fd, &pfn_flags)) >+ return 0; >+ if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL))) >+ return 0; >+ } If this folio is larger than order, would it still return 1? >+ return 1; > } > > static void write_file(const char *path, const char *buf, size_t buflen) >@@ -233,7 +259,7 @@ void split_pte_mapped_thp(void) > thp_size = 0; > for (i = 0; i < pagesize * 4; i++) > if (i % pagesize == 0 && >- is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd)) >+ is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) > thp_size++; > > if (thp_size != 4) >@@ -250,7 +276,7 @@ void split_pte_mapped_thp(void) > ksft_exit_fail_msg("%ld byte corrupted\n", i); > > if (i % pagesize == 0 && >- is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd)) >+ !is_backed_by_folio(&pte_mapped[i], 0, pagemap_fd, kpageflags_fd)) > thp_size++; > } > >@@ -522,7 +548,6 @@ int main(int argc, char **argv) > const char *fs_loc; > bool created_tmp; > int offset; >- unsigned int max_order; > unsigned int nr_pages; > unsigned int tests; > >@@ -543,28 +568,28 @@ int main(int argc, char **argv) > ksft_exit_fail_msg("Reading PMD pagesize failed\n"); > > nr_pages = pmd_pagesize / pagesize; >- max_order = GET_ORDER(nr_pages); >- tests = 2 + (max_order - 1) + (2 * max_order) + (max_order - 1) * 4 + 2; >+ pmd_order = GET_ORDER(nr_pages); >+ tests = 2 + (pmd_order - 1) + (2 * pmd_order) + (pmd_order - 1) * 4 + 2; > ksft_set_plan(tests); > > fd_size = 2 * pmd_pagesize; > > split_pmd_zero_pages(); > >- for (i = 0; i < max_order; i++) >+ for (i = 0; i < pmd_order; i++) > if (i != 1) > split_pmd_thp_to_order(i); > > split_pte_mapped_thp(); >- for (i = 0; i < max_order; i++) >+ for (i = 0; i < pmd_order; i++) > split_file_backed_thp(i); > > created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template, > &fs_loc); >- for (i = max_order - 1; i >= 0; i--) >+ for (i = pmd_order - 1; i >= 0; i--) > split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1); > >- for (i = 0; i < max_order; i++) >+ for (i = 0; i < pmd_order; i++) > for (offset = 0; > offset < nr_pages; > offset += MAX(nr_pages / 4, 1 << i)) >diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c >index 4d952d1bc96d..193ba1a1a3cc 100644 >--- a/tools/testing/selftests/mm/vm_util.c >+++ b/tools/testing/selftests/mm/vm_util.c >@@ -338,7 +338,7 @@ int detect_hugetlb_page_sizes(size_t sizes[], int max) > return count; > } > >-static int get_pfn_flags(unsigned long pfn, int kpageflags_fd, uint64_t *flags) >+int get_pfn_flags(unsigned long pfn, int kpageflags_fd, uint64_t *flags) > { > size_t count; > >diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h >index 02e3f1e7065b..148b792cff0f 100644 >--- a/tools/testing/selftests/mm/vm_util.h >+++ b/tools/testing/selftests/mm/vm_util.h >@@ -92,6 +92,7 @@ unsigned long default_huge_page_size(void); > int detect_hugetlb_page_sizes(size_t sizes[], int max); > int check_folio_orders(char *vaddr_start, size_t len, int pagemap_file, > int kpageflags_file, int orders[], int nr_orders); >+int get_pfn_flags(unsigned long pfn, int kpageflags_fd, uint64_t *flags); > > int uffd_register(int uffd, void *addr, uint64_t len, > bool miss, bool wp, bool minor); >-- >2.47.2 -- Wei Yang Help you, Help me