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Message-ID: <d90d8aa9-0e19-4098-ad3c-1c8069167538@linux.ibm.com>
Date: Sun, 10 Aug 2025 22:23:24 +0530
From: Donet Tom <donettom@...ux.ibm.com>
To: Zi Yan <ziy@...dia.com>, 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
Cc: 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 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?
> 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;
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