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Message-ID: <20250818184622.1521620-6-ziy@nvidia.com>
Date: Mon, 18 Aug 2025 14:46:22 -0400
From: Zi Yan <ziy@...dia.com>
To: 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>,
Zi Yan <ziy@...dia.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: [PATCH v5 5/5] selftests/mm: check after-split folio orders in split_huge_page_test.
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 split ranges in split_thp_in_pagecache_to_order_at() are changed to
[addr, addr + pagesize) for every pmd_pagesize. It prevents folios within
the range being split multiple times due to debugfs split function always
perform splits with a pagesize step for a given range.
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 | 88 ++++++++++++++-----
1 file changed, 64 insertions(+), 24 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index e24df02420ad..a66ecbdfe7c6 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -26,6 +26,7 @@ uint64_t pagesize;
unsigned int pageshift;
uint64_t pmd_pagesize;
unsigned int pmd_order;
+int *expected_orders;
#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
#define SMAP_PATH "/proc/self/smaps"
@@ -35,6 +36,11 @@ unsigned int pmd_order;
#define PID_FMT_OFFSET "%d,0x%lx,0x%lx,%d,%d"
#define PATH_FMT "%s,0x%lx,0x%lx,%d"
+const char *pagemap_proc = "/proc/self/pagemap";
+const char *kpageflags_proc = "/proc/kpageflags";
+int pagemap_fd;
+int kpageflags_fd;
+
static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
int kpageflags_fd)
{
@@ -366,6 +372,13 @@ static void split_pmd_thp_to_order(int order)
if (one_page[i] != (char)i)
ksft_exit_fail_msg("%ld byte corrupted\n", i);
+ memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+ expected_orders[order] = 4 << (pmd_order - order);
+
+ if (check_after_split_folio_orders(one_page, len, pagemap_fd,
+ kpageflags_fd, expected_orders,
+ (pmd_order + 1)))
+ 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");
@@ -380,22 +393,6 @@ static 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);
@@ -453,8 +450,6 @@ static 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);
}
static void split_file_backed_thp(int order)
@@ -657,6 +652,7 @@ static 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];
@@ -670,14 +666,33 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
if (err)
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(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+ /*
+ * use [split_addr, split_addr + pagesize) range to split THPs, since
+ * the debugfs function always split a range with pagesize step and
+ * providing a full [addr, addr + fd_size) range can trigger multiple
+ * splits, complicating after-split result checking.
+ */
+ 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);
+
+ expected_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);
+
+ for (i = order + 1; i < pmd_order; i++)
+ expected_orders[i] = times;
+ expected_orders[order] = 2 * times;
+ }
for (i = 0; i < fd_size; i++)
if (*(addr + i) != (char)i) {
@@ -686,6 +701,14 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
goto out;
}
+ if (check_after_split_folio_orders(addr, fd_size, pagemap_fd,
+ kpageflags_fd, expected_orders,
+ (pmd_order + 1))) {
+ 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;
@@ -737,9 +760,22 @@ int main(int argc, char **argv)
nr_pages = pmd_pagesize / pagesize;
pmd_order = sz2ord(pmd_pagesize, pagesize);
+
+ expected_orders = (int *)malloc(sizeof(int) * (pmd_order + 1));
+ if (!expected_orders)
+ ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
+
tests = 2 + (pmd_order - 1) + (2 * pmd_order) + (pmd_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();
@@ -764,6 +800,10 @@ 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);
+ free(expected_orders);
+
ksft_finished();
return 0;
--
2.50.1
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