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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 v8 3/4] kselftest: mm: integrate huge page checks Message-ID: References: <20260924-fix_split-v8-0-cba7359d882a@arm.com> <20260924-fix_split-v8-3-cba7359d882a@arm.com> <16f16e77-05ab-418e-ad06-8f48fb29375a@kernel.org> <3e03425b-7962-4c69-93aa-96168fd7168e@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e03425b-7962-4c69-93aa-96168fd7168e@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3F7EF1C0003 X-Stat-Signature: 4hjooiijtokepq5w9mhgn869cubhaetp X-HE-Tag: 1790862732-729852 X-HE-Meta: U2FsdGVkX1+ywex8L2zt8ZipP5WVLmntQzgImM3a20Oj7Z5ImBm0HnnnzgZDS4mcGx/wTAXLrRJPPCNl9KJTcIM3ycLqBWA7PzoEuIWVCns6zuKFNFoBIBDeIafErJm8OavpR9HNlEvtjmCxobIGCxBjiVqOLWdG0sGI8B+qFMprjNCfYFUip3flME0eiXHdvJiUuoNsoDeh53NkooAl/M/0DaHdg80mmWdP+MGkF3tyrXeu99e1QMbxgS/cQtd1tE3Dby90Oxz8I1XNzTdlJzHBIUfNQUqDYR48qMYots4I8lzlKORMrCvo3vPcktnxGnikK9mELphYHdLGxqcxJqsAEfEknYEXQLwNMHaRykDIk2VwOBkqSjtAr9qH4h+ennssUPuhoWVmlb33SK2pzDsXzI6r8KRx9iqU69dkJJjBHEtlxNK928K8JDX/dzHp3fk5PAv89GjOLnkqIvFM+/kMO7iFOB05+HYRnfdRHKBVocebRKrmRRjvTxtsOyv4spcUMLxs3tL8xXr9j9K2REvjd7pvNxx3zv+0k//kvu3W9JmaYPPaPtybrq5TVJAT0stqLHas5K2Hio/3ca/wBHF9PGIdH5Iq1Ys2Ad+p4+KsHa/V5e+Gji0bhWmqXPPuMMN1O6955fNrZfy83yHZ+YOMl+lGbPv6eKHd+6GTJa7UZof7qaBWpz2ZZHQabmJu/tZZtmiZ9JhK80gndk/YxAROfCePrxba3ZBA2Jn9jJAXuUcT16Q+aaW9RGHlXAhrVM26158EFabQjrj20Yu76YhYQnPTs90/2CHgqWKUzfU0rle3p3nXvP9KNgudfHERkyaa5CYMh+bijqC01NwNaAmcOckJklp3sSt/a4RDxrSgFJOsrEurDA9lZYZtzQL7ZgrKt3tvQORGflSY42qaR4Gs0gprKtmAKtXrqKPlJ1jW2dxEP5roxVAr28biIcs6xwgMORVkq77C70l+gBV /rNahnt8 KRDjIuzJ9T2yN7+vEajlmMKbmRFBRfTMnFu/T7quFPW8ykMYwZKmDSDvYh85JnN6njShVBzMFUH6AfATc5a/M0gGWpQpqOpTDulZe5Z0zuOKxyb9F9mjsppOvGafyL1HYcs+S4Lr3IcqOcw1nufl7cKU1DrkYUiKKe/LL1M3eTsxBPo8Ib4GbXIjg6wKgstB7OtH+Sg+l8hx1f3+BUYSURF3SuyTdTHsoQAZwGlcZnDY0DY2QUnF/UCqRSU1FHTLRdZogQPuRNiU7CfG0ZmFD+Y5M3q6IK3wPcPVzG6HgmMs9Q20hsWLZ8EEIvJzdNoE/o6pJJzy1XDPsXiam561HI0Ndmw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On 9/29/26 12:01, Yeoreum Yun wrote: > > On Tue, Sep 29, 2026 at 10:07:37AM +0200, David Hildenbrand (Arm) wrote: > >> On 9/24/26 21:11, Yeoreum Yun wrote: > >>> check_large_folios() only checks for large folios without distinguishing > >>> between anonymous and file-backed huge pages. > >>> > >>> To add huge page type checking, integrate the huge page checks into > >>> __check_huge(): > >>> > >>> 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 huge page type. > >>> > >>> Suggested-by: David Hildenbrand (Arm) > >>> Suggested-by: Zi Yan > >>> Signed-off-by: Yeoreum Yun > >>> --- > >> > >> Instead of merging both things (detecting mapping vs. detecting anon vs. file), > >> could we simply perform the anon vs. file change separately? > >> > >> Doing another pagemap walk that focuses on that should end up with something > >> that is easier to read. > > > > Okay. I'll change like below in next-spin: > > > > -------&<------- > > > > @@ -411,57 +400,78 @@ static bool check_huge_type(uint64_t categories, enum check_huge_type type) > > return false; > > } > > > > -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; > > + bool ret = false; > > + int pagemap_fd, kpageflags_fd; > > int nr_pmd_mappings = 0; > > + uint64_t pmd_pagesize, scan_mapping_size; > > uint64_t categories; > > + 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"); > > + > > + 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; > > + > > pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > > if (pagemap_fd < 0) > > ksft_exit_fail_perror("open pagemap"); > > > > - for (; start < end; start += hpage_size) { > > + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > > + if (kpageflags_fd < 0) > > + ksft_exit_fail_perror("open kpageflags"); > > + > > + for (; start < end; start += scan_mapping_size) { > > categories = pagemap_scan_get_categories(pagemap_fd, start); > > - if (!(categories & PAGE_IS_HUGE)) > > + pfn = pagemap_get_pfn(pagemap_fd, start); > > + if (pfn == -1UL) { > > + if (!allow_nonpresent) > > + goto out; > > continue; > > - if (check_huge_type(categories, type)) > > + } > > + if (!check_huge_type(categories, type)) > > + goto out; > > + } > > + > > + if (!check_pmd_mapping) { > > + ret = check_large_folios(pagemap_fd, kpageflags_fd, > > + addr, len, nr_hpages, hpage_size); > > + goto out; > > + } > > + > > + for (start = addr; start < end; start += scan_mapping_size) { > > + categories = pagemap_scan_get_categories(pagemap_fd, start); > > + if (categories & PAGE_IS_HUGE) > > nr_pmd_mappings++; > > } > > - close(pagemap_fd); > > > > - return nr_hpages == nr_pmd_mappings; > > + if (nr_pmd_mappings != nr_hpages) > > + goto out; > > + ret = true; > > + > > +out: > > + close(pagemap_fd); > > + close(kpageflags_fd); > > + return ret; > > } > > > > I'd leave existing __check_huge() mostly alone, and instead have an additional > function that checks the type. > > Essentially a __check_type() or sth that we run after the large folio / pmd check. So, You mean like this? -------&<------- -enum check_huge_type { - CHECK_HUGE_ANON, - CHECK_HUGE_FILE, +enum check_type { + CHECK_TYPE_ANON, + CHECK_TYPE_FILE, }; -static bool check_huge_type(uint64_t categories, enum check_huge_type type) +static bool __check_type(void *addr, size_t len, uint64_t page_size, + bool allow_nonpresent, enum check_type type) { - const bool file = categories & PAGE_IS_FILE; + bool ret = false; + int pagemap_fd, kpageflags_fd; + char *start = addr; + char *end = start + len; + uint64_t categories; + unsigned long pfn; + + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); + if (pagemap_fd < 0) + ksft_exit_fail_perror("open pagemap"); + + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); + if (kpageflags_fd < 0) + ksft_exit_fail_perror("open kpageflags"); - switch (type) { - case CHECK_HUGE_ANON: - return !file; - case CHECK_HUGE_FILE: - return file; + for (; start < end; start += page_size) { + categories = pagemap_scan_get_categories(pagemap_fd, start); + pfn = pagemap_get_pfn(pagemap_fd, start); + if (pfn == -1UL) { + if (!allow_nonpresent) + goto out; + continue; + } + + if ((type == CHECK_TYPE_FILE) != !!(categories & PAGE_IS_FILE)) + goto out; } - return false; + ret = true; + +out: + close(kpageflags_fd); + close(pagemap_fd); + return ret; } -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) { + bool ret = false; int pagemap_fd; int nr_pmd_mappings = 0; + uint64_t pmd_pagesize; uint64_t categories; char *start = addr; char *end = start + len; + pmd_pagesize = read_pmd_pagesize(); + 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_perror("open pagemap"); - for (; start < end; start += hpage_size) { + if (hpage_size != pmd_pagesize) { + ret = check_large_folios(addr, len, nr_hpages, hpage_size); + goto out; + } + + for (start = addr; start < end; start += hpage_size) { categories = pagemap_scan_get_categories(pagemap_fd, start); - if (!(categories & PAGE_IS_HUGE)) - continue; - if (check_huge_type(categories, type)) + if (categories & PAGE_IS_HUGE) nr_pmd_mappings++; } - close(pagemap_fd); - return nr_hpages == nr_pmd_mappings; + if (nr_pmd_mappings != nr_hpages) + goto out; + + ret = true; + +out: + close(pagemap_fd); + return ret; } 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"); + /* Some mTHP tests check a partially populated PMD-sized range. */ + const bool allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len; + const uint64_t scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize(); - if (hpage_size == pmd_pagesize) - return __check_pmd_huge(addr, len, nr_hpages, hpage_size, - CHECK_HUGE_ANON); + if (! __check_huge(addr, len, nr_hpages, hpage_size)) + return false; - return check_large_folios(addr, len, nr_hpages, hpage_size); + return __check_type(addr, len, scan_mapping_size, allow_nonpresent, + CHECK_TYPE_ANON); } bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) { - uint64_t pmd_pagesize = read_pmd_pagesize(); + /* Some mTHP tests check a partially populated PMD-sized range. */ + const bool allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len; + const uint64_t scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize(); - if (!pmd_pagesize) - ksft_exit_fail_msg("reading PMD pagesize failed\n"); - - if (hpage_size == pmd_pagesize) - return __check_pmd_huge(addr, len, nr_hpages, hpage_size, - CHECK_HUGE_FILE); + if (! __check_huge(addr, len, nr_hpages, hpage_size)) + return false; - return check_large_folios(addr, len, nr_hpages, hpage_size); + return __check_type(addr, len, scan_mapping_size, allow_nonpresent, + CHECK_TYPE_FILE); } -- Sincerely, Yeoreum Yun