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Message-ID: <C15363CE-F4DB-4747-B51C-A8B5673DEBFF@nvidia.com>
Date: Mon, 11 Aug 2025 14:20:11 -0400
From: Zi Yan <ziy@...dia.com>
To: Donet Tom <donettom@...ux.ibm.com>
Cc: Wei Yang <richard.weiyang@...il.com>, wang lian <lianux.mm@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
Barry Song <baohua@...nel.org>, Vlastimil Babka <vbabka@...e.cz>,
Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
Michal Hocko <mhocko@...e.com>, Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 3/3] selftests/mm: check after-split folio orders in
split_huge_page_test.
On 10 Aug 2025, at 12:53, Donet Tom wrote:
> On 8/9/25 12:31 AM, Zi Yan wrote:
>> Instead of just checking the existence of PMD folios before and after folio
>> split tests, use check_folio_orders() to check after-split folio orders.
>>
>> The following tests are not changed:
>> 1. split_pte_mapped_thp: the test already uses kpageflags to check;
>> 2. split_file_backed_thp: no vaddr available.
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> ---
>> .../selftests/mm/split_huge_page_test.c | 98 ++++++++++++++-----
>> 1 file changed, 72 insertions(+), 26 deletions(-)
>>
>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
>> index 5ab488fab1cd..161108717f1c 100644
>> --- a/tools/testing/selftests/mm/split_huge_page_test.c
>> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
>> @@ -25,6 +25,10 @@
>> uint64_t pagesize;
>> unsigned int pageshift;
>> uint64_t pmd_pagesize;
>> +unsigned int pmd_order;
>> +unsigned int max_order;
>> +
>> +#define NR_ORDERS (max_order + 1)
>> #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
>> #define SMAP_PATH "/proc/self/smaps"
>> @@ -36,6 +40,11 @@ uint64_t pmd_pagesize;
>> #define GET_ORDER(nr_pages) (31 - __builtin_clz(nr_pages))
>> +const char *pagemap_proc = "/proc/self/pagemap";
>> +const char *kpageflags_proc = "/proc/kpageflags";
>> +int pagemap_fd;
>> +int kpageflags_fd;
>> +
>> int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
>> {
>> uint64_t paddr;
>> @@ -151,6 +160,11 @@ void split_pmd_thp_to_order(int order)
>> char *one_page;
>> size_t len = 4 * pmd_pagesize;
>> size_t i;
>> + int *orders;
>> +
>> + orders = (int *)malloc(sizeof(int) * NR_ORDERS);
>> + if (!orders)
>> + ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
>> one_page = memalign(pmd_pagesize, len);
>> if (!one_page)
>> @@ -172,12 +186,20 @@ void split_pmd_thp_to_order(int order)
>> if (one_page[i] != (char)i)
>> ksft_exit_fail_msg("%ld byte corrupted\n", i);
>> + memset(orders, 0, sizeof(int) * NR_ORDERS);
>> + /* set expected orders */
>> + orders[order] = 4 << (pmd_order - order);
>> +
>> + if (check_folio_orders(one_page, len, pagemap_fd, kpageflags_fd,
>> + orders, NR_ORDERS))
>> + ksft_exit_fail_msg("Unexpected THP split\n");
>> if (!check_huge_anon(one_page, 0, pmd_pagesize))
>> ksft_exit_fail_msg("Still AnonHugePages not split\n");
>> ksft_test_result_pass("Split huge pages to order %d successful\n", order);
>> free(one_page);
>> + free(orders);
>> }
>> void split_pte_mapped_thp(void)
>> @@ -186,22 +208,6 @@ void split_pte_mapped_thp(void)
>> size_t len = 4 * pmd_pagesize;
>> uint64_t thp_size;
>> size_t i;
>> - const char *pagemap_template = "/proc/%d/pagemap";
>> - const char *kpageflags_proc = "/proc/kpageflags";
>> - char pagemap_proc[255];
>> - int pagemap_fd;
>> - int kpageflags_fd;
>> -
>> - if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0)
>> - ksft_exit_fail_msg("get pagemap proc error: %s\n", strerror(errno));
>> -
>> - pagemap_fd = open(pagemap_proc, O_RDONLY);
>> - if (pagemap_fd == -1)
>> - ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
>> -
>> - kpageflags_fd = open(kpageflags_proc, O_RDONLY);
>> - if (kpageflags_fd == -1)
>> - ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
>> one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
>> MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>> @@ -259,8 +265,6 @@ void split_pte_mapped_thp(void)
>> ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
>> munmap(one_page, len);
>> - close(pagemap_fd);
>> - close(kpageflags_fd);
>> }
>> void split_file_backed_thp(int order)
>> @@ -463,10 +467,16 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>> int order, int offset)
>> {
>> int fd;
>> + char *split_addr;
>> char *addr;
>> size_t i;
>> char testfile[INPUT_MAX];
>> int err = 0;
>> + int *orders;
>> +
>> + orders = (int *)malloc(sizeof(int) * NR_ORDERS);
>> + if (!orders)
>> + ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
>> err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
>> @@ -474,16 +484,32 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>> ksft_exit_fail_msg("cannot generate right test file name\n");
>> err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
>> - if (err)
>> + if (err) {
>> + free(orders);
>> return;
>> + }
>> err = 0;
>> - if (offset == -1)
>> - write_debugfs(PID_FMT, getpid(), (uint64_t)addr,
>> - (uint64_t)addr + fd_size, order);
>> - else
>> - write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)addr,
>> - (uint64_t)addr + fd_size, order, offset);
>> + memset(orders, 0, sizeof(int) * NR_ORDERS);
>> + if (offset == -1) {
>> + for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
>> + write_debugfs(PID_FMT, getpid(), (uint64_t)split_addr,
>> + (uint64_t)split_addr + pagesize, order);
>> +
>> + /* set expected orders */
>> + orders[order] = fd_size / (pagesize << order);
>> + } else {
>> + int times = fd_size / pmd_pagesize;
>> +
>> + for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
>> + write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)split_addr,
>> + (uint64_t)split_addr + pagesize, order, offset);
>> +
>> + /* set expected orders */
>> + for (i = order + 1; i < pmd_order; i++)
>> + orders[i] = times;
>> + orders[order] = 2 * times;
>> + }
>> for (i = 0; i < fd_size; i++)
>> if (*(addr + i) != (char)i) {
>> @@ -492,6 +518,14 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>> goto out;
>> }
>> + if (check_folio_orders(addr, fd_size, pagemap_fd, kpageflags_fd, orders,
>> + NR_ORDERS)) {
>> + ksft_print_msg("Unexpected THP split\n");
>> + err = 1;
>> + goto out;
>> + }
>> +
>> +
>> if (!check_huge_file(addr, 0, pmd_pagesize)) {
>> ksft_print_msg("Still FilePmdMapped not split\n");
>> err = EXIT_FAILURE;
>> @@ -499,6 +533,7 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>> }
>> out:
>> + free(orders);
>> munmap(addr, fd_size);
>> close(fd);
>> unlink(testfile);
>> @@ -522,7 +557,6 @@ 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;
>> @@ -539,6 +573,7 @@ int main(int argc, char **argv)
>> pagesize = getpagesize();
>> pageshift = ffs(pagesize) - 1;
>> pmd_pagesize = read_pmd_pagesize();
>> + pmd_order = GET_ORDER(pmd_pagesize / pagesize);
>
>
> I think max_order is also same as pmd_order
>
> nr_pages = pmd_pagesize / pagesize;
> max_order = GET_ORDER(nr_pages);
>
> Can we use one?
Sure. Will rename max_order to pmd_order. Thanks.
>
>> if (!pmd_pagesize)
>> ksft_exit_fail_msg("Reading PMD pagesize failed\n");
>> @@ -547,6 +582,14 @@ int main(int argc, char **argv)
>> tests = 2 + (max_order - 1) + (2 * max_order) + (max_order - 1) * 4 + 2;
>> ksft_set_plan(tests);
>> + pagemap_fd = open(pagemap_proc, O_RDONLY);
>> + if (pagemap_fd == -1)
>> + ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
>> +
>> + kpageflags_fd = open(kpageflags_proc, O_RDONLY);
>> + if (kpageflags_fd == -1)
>> + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
>> +
>> fd_size = 2 * pmd_pagesize;
>> split_pmd_zero_pages();
>> @@ -571,6 +614,9 @@ int main(int argc, char **argv)
>> split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, offset);
>> cleanup_thp_fs(fs_loc, created_tmp);
>> + close(pagemap_fd);
>> + close(kpageflags_fd);
>> +
>> ksft_finished();
>> return 0;
Best Regards,
Yan, Zi
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