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Message-ID: <20251007182935207jm31wCIgLpZg5XbXQY64S@zte.com.cn>
Date: Tue, 7 Oct 2025 18:29:35 +0800 (CST)
From: <xu.xin16@....com.cn>
To: <xu.xin16@....com.cn>, <akpm@...ux-foundation.org>, <david@...hat.com>,
<tujinjiang@...wei.com>, <shr@...kernel.io>
Cc: <akpm@...ux-foundation.org>, <david@...hat.com>, <tujinjiang@...wei.com>,
<shr@...kernel.io>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
<yang.yang29@....com.cn>, <wang.yaxin@....com.cn>
Subject: [PATCH linux-next v2 2/2] selftests: update ksm inheritation tests for prctl fork/exec
From: xu xin <xu.xin16@....com.cn>
To reproduce the issue mentioned by [1], this add a setting of pages_to_scan
and sleep_millisecs at the start of test_prctl_fork_exec(). The main change
is just raise the scanning frequency of ksmd.
[1] https://lore.kernel.org/all/202510012256278259zrhgATlLA2C510DMD3qI@zte.com.cn/
Signed-off-by: xu xin <xu.xin16@....com.cn>
---
.../selftests/mm/ksm_functional_tests.c | 57 +++++++++++++++++++
1 file changed, 57 insertions(+)
diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index ac136f04b8d6..95afa5cfc062 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -38,6 +38,8 @@ enum ksm_merge_mode {
};
static int mem_fd;
+static int pages_to_scan_fd;
+static int sleep_millisecs_fd;
static int pagemap_fd;
static size_t pagesize;
@@ -493,6 +495,46 @@ static void test_prctl_fork(void)
ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
}
+static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms)
+{
+ int ksm_fd;
+
+ ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+ if (ksm_fd < 0)
+ return -errno;
+
+ if (write(ksm_fd, "1", 1) != 1)
+ return -errno;
+
+ if (write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)) <= 0)
+ return -errno;
+
+ if (write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0)
+ return -errno;
+
+ return 0;
+}
+
+static int stop_ksmd_and_restore_frequency(void)
+{
+ int ksm_fd;
+
+ ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+ if (ksm_fd < 0)
+ return -errno;
+
+ if (write(ksm_fd, "2", 1) != 1)
+ return -errno;
+
+ if (write(pages_to_scan_fd, "100", 3) <= 0)
+ return -errno;
+
+ if (write(sleep_millisecs_fd, "20", 2) <= 0)
+ return -errno;
+
+ return 0;
+}
+
static void test_prctl_fork_exec(void)
{
int ret, status;
@@ -500,6 +542,9 @@ static void test_prctl_fork_exec(void)
ksft_print_msg("[RUN] %s\n", __func__);
+ if (start_ksmd_and_set_frequency("2000", "0"))
+ ksft_test_result_fail("set ksmd's scanning frequency failed\n");
+
ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
if (ret < 0 && errno == EINVAL) {
ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
@@ -542,6 +587,11 @@ static void test_prctl_fork_exec(void)
return;
}
+ if (stop_ksmd_and_restore_frequency()) {
+ ksft_test_result_fail("restore ksmd frequency failed\n");
+ return;
+ }
+
ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
}
@@ -656,6 +706,13 @@ static void init_global_file_handles(void)
ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
if (ksm_get_self_merging_pages() < 0)
ksft_exit_skip("accessing \"/proc/self/ksm_merging_pages\") failed\n");
+
+ pages_to_scan_fd = open("/sys/kernel/mm/ksm/pages_to_scan", O_RDWR);
+ if (pages_to_scan_fd < 0)
+ ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/pages_to_scan failed\n");
+ sleep_millisecs_fd = open("/sys/kernel/mm/ksm/sleep_millisecs", O_RDWR);
+ if (sleep_millisecs_fd < 0)
+ ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/sleep_millisecs failed\n");
}
int main(int argc, char **argv)
--
2.25.1
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