Re: [Patch v2 1/2] selftests/mm: put general ksm operation into vm_util

[Wei Yang <richard.weiyang@gmail.com>]

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On Sat, Jul 26, 2025 at 02:52:22AM +0000, Wei Yang wrote:
>There are some general ksm operations could be used by other related
>test case. Put them into vm_util for common use.
>
>This is a preparation patch for later use.
>
>Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>Suggested-by: David Hildenbrand <david@redhat.com>
>Cc: David Hildenbrand <david@redhat.com>
>Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>Cc: Rik van Riel <riel@surriel.com>
>Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
>Cc: Vlastimil Babka <vbabka@suse.cz>
>Cc: Harry Yoo <harry.yoo@oracle.com>
>
>---
>v2:
>  * do check on file opening in init_global_file_handlers()
>  * factor out ksm_merge() and ksm_unmerge() instead of partial of it
>  * align the return value of helpers: 0 on success, -errno on error
>v1: open/close fd in function itself instead of pass as parameter
>---
> .../selftests/mm/ksm_functional_tests.c       | 128 +++---------------
> tools/testing/selftests/mm/vm_util.c          | 123 +++++++++++++++++
> tools/testing/selftests/mm/vm_util.h          |   7 +
> 3 files changed, 147 insertions(+), 111 deletions(-)
>
>diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
>index d8bd1911dfc0..bab74455d70b 100644
>--- a/tools/testing/selftests/mm/ksm_functional_tests.c
>+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
>@@ -38,11 +38,6 @@ enum ksm_merge_mode {
> };
> 
> static int mem_fd;
>-static int ksm_fd;
>-static int ksm_full_scans_fd;
>-static int proc_self_ksm_stat_fd;
>-static int proc_self_ksm_merging_pages_fd;
>-static int ksm_use_zero_pages_fd;
> static int pagemap_fd;
> static size_t pagesize;
> 
>@@ -73,88 +68,6 @@ static bool range_maps_duplicates(char *addr, unsigned long size)
> 	return false;
> }
> 
>-static long get_my_ksm_zero_pages(void)
>-{
>-	char buf[200];
>-	char *substr_ksm_zero;
>-	size_t value_pos;
>-	ssize_t read_size;
>-	unsigned long my_ksm_zero_pages;
>-
>-	if (!proc_self_ksm_stat_fd)
>-		return 0;
>-
>-	read_size = pread(proc_self_ksm_stat_fd, buf, sizeof(buf) - 1, 0);
>-	if (read_size < 0)
>-		return -errno;
>-
>-	buf[read_size] = 0;
>-
>-	substr_ksm_zero = strstr(buf, "ksm_zero_pages");
>-	if (!substr_ksm_zero)
>-		return 0;
>-
>-	value_pos = strcspn(substr_ksm_zero, "0123456789");
>-	my_ksm_zero_pages = strtol(substr_ksm_zero + value_pos, NULL, 10);
>-
>-	return my_ksm_zero_pages;
>-}
>-
>-static long get_my_merging_pages(void)
>-{
>-	char buf[10];
>-	ssize_t ret;
>-
>-	if (proc_self_ksm_merging_pages_fd < 0)
>-		return proc_self_ksm_merging_pages_fd;
>-
>-	ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
>-	if (ret <= 0)
>-		return -errno;
>-	buf[ret] = 0;
>-
>-	return strtol(buf, NULL, 10);
>-}
>-
>-static long ksm_get_full_scans(void)
>-{
>-	char buf[10];
>-	ssize_t ret;
>-
>-	ret = pread(ksm_full_scans_fd, buf, sizeof(buf) - 1, 0);
>-	if (ret <= 0)
>-		return -errno;
>-	buf[ret] = 0;
>-
>-	return strtol(buf, NULL, 10);
>-}
>-
>-static int ksm_merge(void)
>-{
>-	long start_scans, end_scans;
>-
>-	/* Wait for two full scans such that any possible merging happened. */
>-	start_scans = ksm_get_full_scans();
>-	if (start_scans < 0)
>-		return start_scans;
>-	if (write(ksm_fd, "1", 1) != 1)
>-		return -errno;
>-	do {
>-		end_scans = ksm_get_full_scans();
>-		if (end_scans < 0)
>-			return end_scans;
>-	} while (end_scans < start_scans + 2);
>-
>-	return 0;
>-}
>-
>-static int ksm_unmerge(void)
>-{
>-	if (write(ksm_fd, "2", 1) != 1)
>-		return -errno;
>-	return 0;
>-}
>-
> static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
> 				  enum ksm_merge_mode mode)
> {
>@@ -163,12 +76,12 @@ static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
> 	int ret;
> 
> 	/* Stabilize accounting by disabling KSM completely. */
>-	if (ksm_unmerge()) {
>+	if (ksm_stop() < 0) {
> 		ksft_print_msg("Disabling (unmerging) KSM failed\n");
> 		return err_map;
> 	}
> 
>-	if (get_my_merging_pages() > 0) {
>+	if (ksm_get_self_merging_pages() > 0) {
> 		ksft_print_msg("Still pages merged\n");
> 		return err_map;
> 	}
>@@ -218,7 +131,7 @@ static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
> 	}
> 
> 	/* Run KSM to trigger merging and wait. */
>-	if (ksm_merge()) {
>+	if (ksm_start() < 0) {
> 		ksft_print_msg("Running KSM failed\n");
> 		goto unmap;
> 	}
>@@ -227,7 +140,7 @@ static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
> 	 * Check if anything was merged at all. Ignore the zero page that is
> 	 * accounted differently (depending on kernel support).
> 	 */
>-	if (val && !get_my_merging_pages()) {
>+	if (val && !ksm_get_self_merging_pages()) {
> 		ksft_print_msg("No pages got merged\n");
> 		goto unmap;
> 	}
>@@ -286,15 +199,12 @@ static void test_unmerge_zero_pages(void)
> 
> 	ksft_print_msg("[RUN] %s\n", __func__);
> 
>-	if (proc_self_ksm_stat_fd < 0) {
>-		ksft_test_result_skip("open(\"/proc/self/ksm_stat\") failed\n");
>-		return;
>-	}
>-	if (ksm_use_zero_pages_fd < 0) {
>-		ksft_test_result_skip("open \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
>+	if (ksm_get_self_zero_pages() < 0) {
>+		ksft_test_result_skip("accessing \"/proc/self/ksm_stat\" failed\n");
> 		return;
> 	}
>-	if (write(ksm_use_zero_pages_fd, "1", 1) != 1) {
>+
>+	if (ksm_use_zero_pages() < 0) {
> 		ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
> 		return;
> 	}
>@@ -306,7 +216,7 @@ static void test_unmerge_zero_pages(void)
> 
> 	/* Check if ksm_zero_pages is updated correctly after KSM merging */
> 	pages_expected = size / pagesize;
>-	if (pages_expected != get_my_ksm_zero_pages()) {
>+	if (pages_expected != ksm_get_self_zero_pages()) {
> 		ksft_test_result_fail("'ksm_zero_pages' updated after merging\n");
> 		goto unmap;
> 	}
>@@ -319,7 +229,7 @@ static void test_unmerge_zero_pages(void)
> 
> 	/* Check if ksm_zero_pages is updated correctly after unmerging */
> 	pages_expected /= 2;
>-	if (pages_expected != get_my_ksm_zero_pages()) {
>+	if (pages_expected != ksm_get_self_zero_pages()) {
> 		ksft_test_result_fail("'ksm_zero_pages' updated after unmerging\n");
> 		goto unmap;
> 	}
>@@ -329,7 +239,7 @@ static void test_unmerge_zero_pages(void)
> 		*((unsigned int *)&map[offs]) = offs;
> 
> 	/* Now we should have no zeropages remaining. */
>-	if (get_my_ksm_zero_pages()) {
>+	if (ksm_get_self_zero_pages()) {
> 		ksft_test_result_fail("'ksm_zero_pages' updated after write fault\n");
> 		goto unmap;
> 	}
>@@ -685,19 +595,15 @@ static void init_global_file_handles(void)
> 	mem_fd = open("/proc/self/mem", O_RDWR);
> 	if (mem_fd < 0)
> 		ksft_exit_fail_msg("opening /proc/self/mem failed\n");
>-	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
>-	if (ksm_fd < 0)
>-		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/run\") failed\n");
>-	ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
>-	if (ksm_full_scans_fd < 0)
>-		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/full_scans\") failed\n");
>+	if (ksm_stop() < 0)
>+		ksft_exit_skip("accessing \"/sys/kernel/mm/ksm/run\") failed\n");
>+	if (ksm_get_full_scans() < 0)
>+		ksft_exit_skip("accessing \"/sys/kernel/mm/ksm/full_scans\") failed\n");
> 	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
> 	if (pagemap_fd < 0)
> 		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
>-	proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
>-	proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
>-						O_RDONLY);
>-	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
>+	if (ksm_get_self_merging_pages() < 0)
>+		ksft_exit_skip("accessing \"/proc/self/ksm_merging_pages\") failed\n");
> }
> 
> int main(int argc, char **argv)
>diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
>index 9dafa7669ef9..c0b82e9eaa9f 100644
>--- a/tools/testing/selftests/mm/vm_util.c
>+++ b/tools/testing/selftests/mm/vm_util.c
>@@ -555,3 +555,126 @@ bool detect_huge_zeropage(void)
> 	close(fd);
> 	return enabled;
> }
>+
>+long ksm_get_self_zero_pages(void)
>+{
>+	int proc_self_ksm_stat_fd;
>+	char buf[200];
>+	char *substr_ksm_zero;
>+	size_t value_pos;
>+	ssize_t read_size;
>+
>+	proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
>+	if (proc_self_ksm_stat_fd < 0)
>+		return -errno;
>+
>+	read_size = pread(proc_self_ksm_stat_fd, buf, sizeof(buf) - 1, 0);
>+	close(proc_self_ksm_stat_fd);
>+	if (read_size < 0)
>+		return -errno;
>+
>+	buf[read_size] = 0;
>+
>+	substr_ksm_zero = strstr(buf, "ksm_zero_pages");
>+	if (!substr_ksm_zero)
>+		return 0;
>+
>+	value_pos = strcspn(substr_ksm_zero, "0123456789");
>+	return strtol(substr_ksm_zero + value_pos, NULL, 10);
>+}
>+
>+long ksm_get_self_merging_pages(void)
>+{
>+	int proc_self_ksm_merging_pages_fd;
>+	char buf[10];
>+	ssize_t ret;
>+
>+	proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
>+						O_RDONLY);
>+	if (proc_self_ksm_merging_pages_fd < 0)
>+		return -errno;
>+
>+	ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
>+	close(proc_self_ksm_merging_pages_fd);
>+	if (ret <= 0)
>+		return -errno;
>+	buf[ret] = 0;
>+
>+	return strtol(buf, NULL, 10);
>+}
>+
>+long ksm_get_full_scans(void)
>+{
>+	int ksm_full_scans_fd;
>+	char buf[10];
>+	ssize_t ret;
>+
>+	ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
>+	if (ksm_full_scans_fd < 0)
>+		return -errno;
>+
>+	ret = pread(ksm_full_scans_fd, buf, sizeof(buf) - 1, 0);
>+	close(ksm_full_scans_fd);
>+	if (ret <= 0)
>+		return -errno;
>+	buf[ret] = 0;
>+
>+	return strtol(buf, NULL, 10);
>+}
>+
>+int ksm_use_zero_pages(void)
>+{
>+	int ksm_use_zero_pages_fd;
>+	ssize_t ret;
>+
>+	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
>+	if (ksm_use_zero_pages_fd < 0)
>+		return -errno;
>+
>+	ret = write(ksm_use_zero_pages_fd, "1", 1);
>+	close(ksm_use_zero_pages_fd);
>+	return ret == 1 ? 0 : -errno;
>+}
>+
>+int ksm_start(void)
>+{
>+	int ksm_fd;
>+	ssize_t ret;
>+	long start_scans, end_scans;
>+
>+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
>+	if (ksm_fd < 0)
>+		return -errno;
>+
>+	/* Wait for two full scans such that any possible merging happened. */
>+	start_scans = ksm_get_full_scans();
>+	if (start_scans < 0) {
>+		close(ksm_fd);
>+		return start_scans;
>+	}
>+	ret = write(ksm_fd, "1", 1);
>+	close(ksm_fd);
>+	if (ret != 1)
>+		return -errno;
>+	do {
>+		end_scans = ksm_get_full_scans();
>+		if (end_scans < 0)
>+			return end_scans;
>+	} while (end_scans < start_scans + 2);
>+
>+	return 0;
>+}
>+
>+int ksm_stop(void)
>+{
>+	int ksm_fd;
>+	ssize_t ret;
>+
>+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
>+	if (ksm_fd < 0)
>+		return -errno;
>+
>+	ret = write(ksm_fd, "2", 1);
>+	close(ksm_fd);
>+	return ret == 1 ? 0 : -errno;
>+}
>diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
>index c20298ae98ea..ba84ec17d04a 100644
>--- a/tools/testing/selftests/mm/vm_util.h
>+++ b/tools/testing/selftests/mm/vm_util.h
>@@ -129,6 +129,13 @@ static inline void log_test_result(int result)
> void *sys_mremap(void *old_address, unsigned long old_size,
> 		 unsigned long new_size, int flags, void *new_address);
> 
>+long ksm_get_self_zero_pages(void);
>+long ksm_get_self_merging_pages(void);
>+long ksm_get_full_scans(void);
>+int ksm_use_zero_pages(void);
>+int ksm_start(void);
>+int ksm_stop(void);
>+
> /*
>  * On ppc64 this will only work with radix 2M hugepage size
>  */
>-- 
>2.34.1

-- 
Wei Yang
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