diff mbox series

[v2,1/4] selftests: vm: add KSM merge test

Message ID 90287685c13300972ea84de93d1f3f900373f9fe.1626252248.git.zhansayabagdaulet@gmail.com (mailing list archive)
State New
Headers show
Series add KSM selftests | expand

Commit Message

Zhansaya Bagdauletkyzy July 14, 2021, 8:56 a.m. UTC
Add check_ksm_merge() function to check the basic merging feature of
KSM. First, some number of identical pages are allocated and the
MADV_MERGEABLE advice is given to merge these pages. Then, pages_shared
and pages_sharing values are compared with the expected numbers using
assert_ksm_pages_count() function. The number of pages can be changed
using -p option.

Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
---
 tools/testing/selftests/vm/.gitignore     |   1 +
 tools/testing/selftests/vm/Makefile       |   1 +
 tools/testing/selftests/vm/ksm_tests.c    | 306 ++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh |  16 ++
 4 files changed, 324 insertions(+)
 create mode 100644 tools/testing/selftests/vm/ksm_tests.c

Comments

Pasha Tatashin Aug. 4, 2021, 1:54 a.m. UTC | #1
On Wed, Jul 14, 2021 at 4:56 AM Zhansaya Bagdauletkyzy
<zhansayabagdaulet@gmail.com> wrote:
>
> Add check_ksm_merge() function to check the basic merging feature of
> KSM. First, some number of identical pages are allocated and the
> MADV_MERGEABLE advice is given to merge these pages. Then, pages_shared
> and pages_sharing values are compared with the expected numbers using
> assert_ksm_pages_count() function. The number of pages can be changed
> using -p option.
>
> Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>

No comments, because I have already reviewed this series for Zhansaya
as part of the Outreachy internship, so:

Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Tyler Hicks Aug. 16, 2021, 1:57 p.m. UTC | #2
On 2021-07-14 14:56:06, Zhansaya Bagdauletkyzy wrote:
> Add check_ksm_merge() function to check the basic merging feature of
> KSM. First, some number of identical pages are allocated and the
> MADV_MERGEABLE advice is given to merge these pages. Then, pages_shared
> and pages_sharing values are compared with the expected numbers using
> assert_ksm_pages_count() function. The number of pages can be changed
> using -p option.
> 
> Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

As Pavel mentioned, we went through some private iterations on these
patches with Zhansaya so my review comments have already been addressed.

Tyler

> ---
>  tools/testing/selftests/vm/.gitignore     |   1 +
>  tools/testing/selftests/vm/Makefile       |   1 +
>  tools/testing/selftests/vm/ksm_tests.c    | 306 ++++++++++++++++++++++
>  tools/testing/selftests/vm/run_vmtests.sh |  16 ++
>  4 files changed, 324 insertions(+)
>  create mode 100644 tools/testing/selftests/vm/ksm_tests.c
> 
> diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
> index f0fd80ef17df..b02eac613fdd 100644
> --- a/tools/testing/selftests/vm/.gitignore
> +++ b/tools/testing/selftests/vm/.gitignore
> @@ -27,3 +27,4 @@ hmm-tests
>  memfd_secret
>  local_config.*
>  split_huge_page_test
> +ksm_tests
> diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
> index 521243770f26..e6f22a801b71 100644
> --- a/tools/testing/selftests/vm/Makefile
> +++ b/tools/testing/selftests/vm/Makefile
> @@ -45,6 +45,7 @@ TEST_GEN_FILES += thuge-gen
>  TEST_GEN_FILES += transhuge-stress
>  TEST_GEN_FILES += userfaultfd
>  TEST_GEN_FILES += split_huge_page_test
> +TEST_GEN_FILES += ksm_tests
>  
>  ifeq ($(MACHINE),x86_64)
>  CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh $(CC) ../x86/trivial_32bit_program.c -m32)
> diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
> new file mode 100644
> index 000000000000..d74d5aa34b16
> --- /dev/null
> +++ b/tools/testing/selftests/vm/ksm_tests.c
> @@ -0,0 +1,306 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <sys/mman.h>
> +#include <stdbool.h>
> +#include <time.h>
> +#include <string.h>
> +
> +#include "../kselftest.h"
> +
> +#define KSM_SYSFS_PATH "/sys/kernel/mm/ksm/"
> +#define KSM_FP(s) (KSM_SYSFS_PATH s)
> +#define KSM_SCAN_LIMIT_SEC_DEFAULT 120
> +#define KSM_PAGE_COUNT_DEFAULT 10l
> +#define KSM_PROT_STR_DEFAULT "rw"
> +
> +struct ksm_sysfs {
> +	unsigned long max_page_sharing;
> +	unsigned long merge_across_nodes;
> +	unsigned long pages_to_scan;
> +	unsigned long run;
> +	unsigned long sleep_millisecs;
> +	unsigned long stable_node_chains_prune_millisecs;
> +	unsigned long use_zero_pages;
> +};
> +
> +static int ksm_write_sysfs(const char *file_path, unsigned long val)
> +{
> +	FILE *f = fopen(file_path, "w");
> +
> +	if (!f) {
> +		fprintf(stderr, "f %s\n", file_path);
> +		perror("fopen");
> +		return 1;
> +	}
> +	if (fprintf(f, "%lu", val) < 0) {
> +		perror("fprintf");
> +		return 1;
> +	}
> +	fclose(f);
> +
> +	return 0;
> +}
> +
> +static int ksm_read_sysfs(const char *file_path, unsigned long *val)
> +{
> +	FILE *f = fopen(file_path, "r");
> +
> +	if (!f) {
> +		fprintf(stderr, "f %s\n", file_path);
> +		perror("fopen");
> +		return 1;
> +	}
> +	if (fscanf(f, "%lu", val) != 1) {
> +		perror("fscanf");
> +		return 1;
> +	}
> +	fclose(f);
> +
> +	return 0;
> +}
> +
> +static int str_to_prot(char *prot_str)
> +{
> +	int prot = 0;
> +
> +	if ((strchr(prot_str, 'r')) != NULL)
> +		prot |= PROT_READ;
> +	if ((strchr(prot_str, 'w')) != NULL)
> +		prot |= PROT_WRITE;
> +	if ((strchr(prot_str, 'x')) != NULL)
> +		prot |= PROT_EXEC;
> +
> +	return prot;
> +}
> +
> +static void print_help(void)
> +{
> +	printf("usage: ksm_tests [-h] [-a prot] [-p page_count] [-l timeout]\n");
> +	printf(" -a: specify the access protections of pages.\n"
> +	       "     <prot> must be of the form [rwx].\n"
> +	       "     Default: %s\n", KSM_PROT_STR_DEFAULT);
> +	printf(" -p: specify the number of pages to test.\n"
> +	       "     Default: %ld\n", KSM_PAGE_COUNT_DEFAULT);
> +	printf(" -l: limit the maximum running time (in seconds) for a test.\n"
> +	       "     Default: %d seconds\n", KSM_SCAN_LIMIT_SEC_DEFAULT);
> +
> +	exit(0);
> +}
> +
> +static void  *allocate_memory(void *ptr, int prot, int mapping, char data, size_t map_size)
> +{
> +	void *map_ptr = mmap(ptr, map_size, PROT_WRITE, mapping, -1, 0);
> +
> +	if (!map_ptr) {
> +		perror("mmap");
> +		return NULL;
> +	}
> +	memset(map_ptr, data, map_size);
> +	if (mprotect(map_ptr, map_size, prot)) {
> +		perror("mprotect");
> +		munmap(map_ptr, map_size);
> +		return NULL;
> +	}
> +
> +	return map_ptr;
> +}
> +
> +static int ksm_do_scan(int scan_count, struct timespec start_time, int timeout)
> +{
> +	struct timespec cur_time;
> +	unsigned long cur_scan, init_scan;
> +
> +	if (ksm_read_sysfs(KSM_FP("full_scans"), &init_scan))
> +		return 1;
> +	cur_scan = init_scan;
> +
> +	while (cur_scan < init_scan + scan_count) {
> +		if (ksm_read_sysfs(KSM_FP("full_scans"), &cur_scan))
> +			return 1;
> +		if (clock_gettime(CLOCK_MONOTONIC_RAW, &cur_time)) {
> +			perror("clock_gettime");
> +			return 1;
> +		}
> +		if ((cur_time.tv_sec - start_time.tv_sec) > timeout) {
> +			printf("Scan time limit exceeded\n");
> +			return 1;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int ksm_merge_pages(void *addr, size_t size, struct timespec start_time, int timeout)
> +{
> +	if (madvise(addr, size, MADV_MERGEABLE)) {
> +		perror("madvise");
> +		return 1;
> +	}
> +	if (ksm_write_sysfs(KSM_FP("run"), 1))
> +		return 1;
> +
> +	/* Since merging occurs only after 2 scans, make sure to get at least 2 full scans */
> +	if (ksm_do_scan(2, start_time, timeout))
> +		return 1;
> +
> +	return 0;
> +}
> +
> +static bool assert_ksm_pages_count(long dupl_page_count)
> +{
> +	unsigned long max_page_sharing, pages_sharing, pages_shared;
> +
> +	if (ksm_read_sysfs(KSM_FP("pages_shared"), &pages_shared) ||
> +	    ksm_read_sysfs(KSM_FP("pages_sharing"), &pages_sharing) ||
> +	    ksm_read_sysfs(KSM_FP("max_page_sharing"), &max_page_sharing))
> +		return false;
> +
> +	/*
> +	 * Since there must be at least 2 pages for merging and 1 page can be
> +	 * shared with the limited number of pages (max_page_sharing), sometimes
> +	 * there are 'leftover' pages that cannot be merged. For example, if there
> +	 * are 11 pages and max_page_sharing = 10, then only 10 pages will be
> +	 * merged and the 11th page won't be affected. As a result, when the number
> +	 * of duplicate pages is divided by max_page_sharing and the remainder is 1,
> +	 * pages_shared and pages_sharing values will be equal between dupl_page_count
> +	 * and dupl_page_count - 1.
> +	 */
> +	if (dupl_page_count % max_page_sharing == 1 || dupl_page_count % max_page_sharing == 0) {
> +		if (pages_shared == dupl_page_count / max_page_sharing &&
> +		    pages_sharing == pages_shared * (max_page_sharing - 1))
> +			return true;
> +	} else {
> +		if (pages_shared == (dupl_page_count / max_page_sharing + 1) &&
> +		    pages_sharing == dupl_page_count - pages_shared)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static int ksm_save_def(struct ksm_sysfs *ksm_sysfs)
> +{
> +	if (ksm_read_sysfs(KSM_FP("max_page_sharing"), &ksm_sysfs->max_page_sharing) ||
> +	    ksm_read_sysfs(KSM_FP("merge_across_nodes"), &ksm_sysfs->merge_across_nodes) ||
> +	    ksm_read_sysfs(KSM_FP("sleep_millisecs"), &ksm_sysfs->sleep_millisecs) ||
> +	    ksm_read_sysfs(KSM_FP("pages_to_scan"), &ksm_sysfs->pages_to_scan) ||
> +	    ksm_read_sysfs(KSM_FP("run"), &ksm_sysfs->run) ||
> +	    ksm_read_sysfs(KSM_FP("stable_node_chains_prune_millisecs"),
> +			   &ksm_sysfs->stable_node_chains_prune_millisecs) ||
> +	    ksm_read_sysfs(KSM_FP("use_zero_pages"), &ksm_sysfs->use_zero_pages))
> +		return 1;
> +
> +	return 0;
> +}
> +
> +static int ksm_restore(struct ksm_sysfs *ksm_sysfs)
> +{
> +	if (ksm_write_sysfs(KSM_FP("max_page_sharing"), ksm_sysfs->max_page_sharing) ||
> +	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), ksm_sysfs->merge_across_nodes) ||
> +	    ksm_write_sysfs(KSM_FP("pages_to_scan"), ksm_sysfs->pages_to_scan) ||
> +	    ksm_write_sysfs(KSM_FP("run"), ksm_sysfs->run) ||
> +	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), ksm_sysfs->sleep_millisecs) ||
> +	    ksm_write_sysfs(KSM_FP("stable_node_chains_prune_millisecs"),
> +			    ksm_sysfs->stable_node_chains_prune_millisecs) ||
> +	    ksm_write_sysfs(KSM_FP("use_zero_pages"), ksm_sysfs->use_zero_pages))
> +		return 1;
> +
> +	return 0;
> +}
> +
> +static int check_ksm_merge(int mapping, int prot, long page_count, int timeout, size_t page_size)
> +{
> +	void *map_ptr;
> +	struct timespec start_time;
> +
> +	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
> +		perror("clock_gettime");
> +		return KSFT_FAIL;
> +	}
> +
> +	/* fill pages with the same data and merge them */
> +	map_ptr = allocate_memory(NULL, prot, mapping, '*', page_size * page_count);
> +	if (!map_ptr)
> +		return KSFT_FAIL;
> +
> +	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
> +		goto err_out;
> +
> +	/* verify that the right number of pages are merged */
> +	if (assert_ksm_pages_count(page_count)) {
> +		printf("OK\n");
> +		munmap(map_ptr, page_size * page_count);
> +		return KSFT_PASS;
> +	}
> +
> +err_out:
> +	printf("Not OK\n");
> +	munmap(map_ptr, page_size * page_count);
> +	return KSFT_FAIL;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int ret, opt;
> +	int prot = 0;
> +	int ksm_scan_limit_sec = KSM_SCAN_LIMIT_SEC_DEFAULT;
> +	long page_count = KSM_PAGE_COUNT_DEFAULT;
> +	size_t page_size = sysconf(_SC_PAGESIZE);
> +	struct ksm_sysfs ksm_sysfs_old;
> +
> +	while ((opt = getopt(argc, argv, "ha:p:l:")) != -1) {
> +		switch (opt) {
> +		case 'a':
> +			prot = str_to_prot(optarg);
> +			break;
> +		case 'p':
> +			page_count = atol(optarg);
> +			if (page_count <= 0) {
> +				printf("The number of pages must be greater than 0\n");
> +				return KSFT_FAIL;
> +			}
> +			break;
> +		case 'l':
> +			ksm_scan_limit_sec = atoi(optarg);
> +			if (ksm_scan_limit_sec <= 0) {
> +				printf("Timeout value must be greater than 0\n");
> +				return KSFT_FAIL;
> +			}
> +			break;
> +		case 'h':
> +			print_help();
> +			break;
> +		default:
> +			return KSFT_FAIL;
> +		}
> +	}
> +
> +	if (prot == 0)
> +		prot = str_to_prot(KSM_PROT_STR_DEFAULT);
> +
> +	if (access(KSM_SYSFS_PATH, F_OK)) {
> +		printf("Config KSM not enabled\n");
> +		return KSFT_SKIP;
> +	}
> +
> +	if (ksm_save_def(&ksm_sysfs_old)) {
> +		printf("Cannot save default tunables\n");
> +		return KSFT_FAIL;
> +	}
> +
> +	if (ksm_write_sysfs(KSM_FP("run"), 2) ||
> +	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), 0) ||
> +	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), 1) ||
> +	    ksm_write_sysfs(KSM_FP("pages_to_scan"), page_count))
> +		return KSFT_FAIL;
> +
> +	ret = check_ksm_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count, ksm_scan_limit_sec,
> +			      page_size);
> +
> +	if (ksm_restore(&ksm_sysfs_old)) {
> +		printf("Cannot restore default tunables\n");
> +		return KSFT_FAIL;
> +	}
> +
> +	return ret;
> +}
> diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
> index d09a6b71f1e9..97b6f712134d 100755
> --- a/tools/testing/selftests/vm/run_vmtests.sh
> +++ b/tools/testing/selftests/vm/run_vmtests.sh
> @@ -377,6 +377,22 @@ else
>  	exitcode=1
>  fi
>  
> +echo "-------------------------------------------------------"
> +echo "running KSM MADV_MERGEABLE test with 10 identical pages"
> +echo "-------------------------------------------------------"
> +./ksm_tests -p 10
> +ret_val=$?
> +
> +if [ $ret_val -eq 0 ]; then
> +	echo "[PASS]"
> +elif [ $ret_val -eq $ksft_skip ]; then
> +	 echo "[SKIP]"
> +	 exitcode=$ksft_skip
> +else
> +	echo "[FAIL]"
> +	exitcode=1
> +fi
> +
>  exit $exitcode
>  
>  exit $exitcode
> -- 
> 2.25.1
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index f0fd80ef17df..b02eac613fdd 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -27,3 +27,4 @@  hmm-tests
 memfd_secret
 local_config.*
 split_huge_page_test
+ksm_tests
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 521243770f26..e6f22a801b71 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -45,6 +45,7 @@  TEST_GEN_FILES += thuge-gen
 TEST_GEN_FILES += transhuge-stress
 TEST_GEN_FILES += userfaultfd
 TEST_GEN_FILES += split_huge_page_test
+TEST_GEN_FILES += ksm_tests
 
 ifeq ($(MACHINE),x86_64)
 CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh $(CC) ../x86/trivial_32bit_program.c -m32)
diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
new file mode 100644
index 000000000000..d74d5aa34b16
--- /dev/null
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -0,0 +1,306 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <sys/mman.h>
+#include <stdbool.h>
+#include <time.h>
+#include <string.h>
+
+#include "../kselftest.h"
+
+#define KSM_SYSFS_PATH "/sys/kernel/mm/ksm/"
+#define KSM_FP(s) (KSM_SYSFS_PATH s)
+#define KSM_SCAN_LIMIT_SEC_DEFAULT 120
+#define KSM_PAGE_COUNT_DEFAULT 10l
+#define KSM_PROT_STR_DEFAULT "rw"
+
+struct ksm_sysfs {
+	unsigned long max_page_sharing;
+	unsigned long merge_across_nodes;
+	unsigned long pages_to_scan;
+	unsigned long run;
+	unsigned long sleep_millisecs;
+	unsigned long stable_node_chains_prune_millisecs;
+	unsigned long use_zero_pages;
+};
+
+static int ksm_write_sysfs(const char *file_path, unsigned long val)
+{
+	FILE *f = fopen(file_path, "w");
+
+	if (!f) {
+		fprintf(stderr, "f %s\n", file_path);
+		perror("fopen");
+		return 1;
+	}
+	if (fprintf(f, "%lu", val) < 0) {
+		perror("fprintf");
+		return 1;
+	}
+	fclose(f);
+
+	return 0;
+}
+
+static int ksm_read_sysfs(const char *file_path, unsigned long *val)
+{
+	FILE *f = fopen(file_path, "r");
+
+	if (!f) {
+		fprintf(stderr, "f %s\n", file_path);
+		perror("fopen");
+		return 1;
+	}
+	if (fscanf(f, "%lu", val) != 1) {
+		perror("fscanf");
+		return 1;
+	}
+	fclose(f);
+
+	return 0;
+}
+
+static int str_to_prot(char *prot_str)
+{
+	int prot = 0;
+
+	if ((strchr(prot_str, 'r')) != NULL)
+		prot |= PROT_READ;
+	if ((strchr(prot_str, 'w')) != NULL)
+		prot |= PROT_WRITE;
+	if ((strchr(prot_str, 'x')) != NULL)
+		prot |= PROT_EXEC;
+
+	return prot;
+}
+
+static void print_help(void)
+{
+	printf("usage: ksm_tests [-h] [-a prot] [-p page_count] [-l timeout]\n");
+	printf(" -a: specify the access protections of pages.\n"
+	       "     <prot> must be of the form [rwx].\n"
+	       "     Default: %s\n", KSM_PROT_STR_DEFAULT);
+	printf(" -p: specify the number of pages to test.\n"
+	       "     Default: %ld\n", KSM_PAGE_COUNT_DEFAULT);
+	printf(" -l: limit the maximum running time (in seconds) for a test.\n"
+	       "     Default: %d seconds\n", KSM_SCAN_LIMIT_SEC_DEFAULT);
+
+	exit(0);
+}
+
+static void  *allocate_memory(void *ptr, int prot, int mapping, char data, size_t map_size)
+{
+	void *map_ptr = mmap(ptr, map_size, PROT_WRITE, mapping, -1, 0);
+
+	if (!map_ptr) {
+		perror("mmap");
+		return NULL;
+	}
+	memset(map_ptr, data, map_size);
+	if (mprotect(map_ptr, map_size, prot)) {
+		perror("mprotect");
+		munmap(map_ptr, map_size);
+		return NULL;
+	}
+
+	return map_ptr;
+}
+
+static int ksm_do_scan(int scan_count, struct timespec start_time, int timeout)
+{
+	struct timespec cur_time;
+	unsigned long cur_scan, init_scan;
+
+	if (ksm_read_sysfs(KSM_FP("full_scans"), &init_scan))
+		return 1;
+	cur_scan = init_scan;
+
+	while (cur_scan < init_scan + scan_count) {
+		if (ksm_read_sysfs(KSM_FP("full_scans"), &cur_scan))
+			return 1;
+		if (clock_gettime(CLOCK_MONOTONIC_RAW, &cur_time)) {
+			perror("clock_gettime");
+			return 1;
+		}
+		if ((cur_time.tv_sec - start_time.tv_sec) > timeout) {
+			printf("Scan time limit exceeded\n");
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+static int ksm_merge_pages(void *addr, size_t size, struct timespec start_time, int timeout)
+{
+	if (madvise(addr, size, MADV_MERGEABLE)) {
+		perror("madvise");
+		return 1;
+	}
+	if (ksm_write_sysfs(KSM_FP("run"), 1))
+		return 1;
+
+	/* Since merging occurs only after 2 scans, make sure to get at least 2 full scans */
+	if (ksm_do_scan(2, start_time, timeout))
+		return 1;
+
+	return 0;
+}
+
+static bool assert_ksm_pages_count(long dupl_page_count)
+{
+	unsigned long max_page_sharing, pages_sharing, pages_shared;
+
+	if (ksm_read_sysfs(KSM_FP("pages_shared"), &pages_shared) ||
+	    ksm_read_sysfs(KSM_FP("pages_sharing"), &pages_sharing) ||
+	    ksm_read_sysfs(KSM_FP("max_page_sharing"), &max_page_sharing))
+		return false;
+
+	/*
+	 * Since there must be at least 2 pages for merging and 1 page can be
+	 * shared with the limited number of pages (max_page_sharing), sometimes
+	 * there are 'leftover' pages that cannot be merged. For example, if there
+	 * are 11 pages and max_page_sharing = 10, then only 10 pages will be
+	 * merged and the 11th page won't be affected. As a result, when the number
+	 * of duplicate pages is divided by max_page_sharing and the remainder is 1,
+	 * pages_shared and pages_sharing values will be equal between dupl_page_count
+	 * and dupl_page_count - 1.
+	 */
+	if (dupl_page_count % max_page_sharing == 1 || dupl_page_count % max_page_sharing == 0) {
+		if (pages_shared == dupl_page_count / max_page_sharing &&
+		    pages_sharing == pages_shared * (max_page_sharing - 1))
+			return true;
+	} else {
+		if (pages_shared == (dupl_page_count / max_page_sharing + 1) &&
+		    pages_sharing == dupl_page_count - pages_shared)
+			return true;
+	}
+
+	return false;
+}
+
+static int ksm_save_def(struct ksm_sysfs *ksm_sysfs)
+{
+	if (ksm_read_sysfs(KSM_FP("max_page_sharing"), &ksm_sysfs->max_page_sharing) ||
+	    ksm_read_sysfs(KSM_FP("merge_across_nodes"), &ksm_sysfs->merge_across_nodes) ||
+	    ksm_read_sysfs(KSM_FP("sleep_millisecs"), &ksm_sysfs->sleep_millisecs) ||
+	    ksm_read_sysfs(KSM_FP("pages_to_scan"), &ksm_sysfs->pages_to_scan) ||
+	    ksm_read_sysfs(KSM_FP("run"), &ksm_sysfs->run) ||
+	    ksm_read_sysfs(KSM_FP("stable_node_chains_prune_millisecs"),
+			   &ksm_sysfs->stable_node_chains_prune_millisecs) ||
+	    ksm_read_sysfs(KSM_FP("use_zero_pages"), &ksm_sysfs->use_zero_pages))
+		return 1;
+
+	return 0;
+}
+
+static int ksm_restore(struct ksm_sysfs *ksm_sysfs)
+{
+	if (ksm_write_sysfs(KSM_FP("max_page_sharing"), ksm_sysfs->max_page_sharing) ||
+	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), ksm_sysfs->merge_across_nodes) ||
+	    ksm_write_sysfs(KSM_FP("pages_to_scan"), ksm_sysfs->pages_to_scan) ||
+	    ksm_write_sysfs(KSM_FP("run"), ksm_sysfs->run) ||
+	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), ksm_sysfs->sleep_millisecs) ||
+	    ksm_write_sysfs(KSM_FP("stable_node_chains_prune_millisecs"),
+			    ksm_sysfs->stable_node_chains_prune_millisecs) ||
+	    ksm_write_sysfs(KSM_FP("use_zero_pages"), ksm_sysfs->use_zero_pages))
+		return 1;
+
+	return 0;
+}
+
+static int check_ksm_merge(int mapping, int prot, long page_count, int timeout, size_t page_size)
+{
+	void *map_ptr;
+	struct timespec start_time;
+
+	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
+		perror("clock_gettime");
+		return KSFT_FAIL;
+	}
+
+	/* fill pages with the same data and merge them */
+	map_ptr = allocate_memory(NULL, prot, mapping, '*', page_size * page_count);
+	if (!map_ptr)
+		return KSFT_FAIL;
+
+	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+		goto err_out;
+
+	/* verify that the right number of pages are merged */
+	if (assert_ksm_pages_count(page_count)) {
+		printf("OK\n");
+		munmap(map_ptr, page_size * page_count);
+		return KSFT_PASS;
+	}
+
+err_out:
+	printf("Not OK\n");
+	munmap(map_ptr, page_size * page_count);
+	return KSFT_FAIL;
+}
+
+int main(int argc, char *argv[])
+{
+	int ret, opt;
+	int prot = 0;
+	int ksm_scan_limit_sec = KSM_SCAN_LIMIT_SEC_DEFAULT;
+	long page_count = KSM_PAGE_COUNT_DEFAULT;
+	size_t page_size = sysconf(_SC_PAGESIZE);
+	struct ksm_sysfs ksm_sysfs_old;
+
+	while ((opt = getopt(argc, argv, "ha:p:l:")) != -1) {
+		switch (opt) {
+		case 'a':
+			prot = str_to_prot(optarg);
+			break;
+		case 'p':
+			page_count = atol(optarg);
+			if (page_count <= 0) {
+				printf("The number of pages must be greater than 0\n");
+				return KSFT_FAIL;
+			}
+			break;
+		case 'l':
+			ksm_scan_limit_sec = atoi(optarg);
+			if (ksm_scan_limit_sec <= 0) {
+				printf("Timeout value must be greater than 0\n");
+				return KSFT_FAIL;
+			}
+			break;
+		case 'h':
+			print_help();
+			break;
+		default:
+			return KSFT_FAIL;
+		}
+	}
+
+	if (prot == 0)
+		prot = str_to_prot(KSM_PROT_STR_DEFAULT);
+
+	if (access(KSM_SYSFS_PATH, F_OK)) {
+		printf("Config KSM not enabled\n");
+		return KSFT_SKIP;
+	}
+
+	if (ksm_save_def(&ksm_sysfs_old)) {
+		printf("Cannot save default tunables\n");
+		return KSFT_FAIL;
+	}
+
+	if (ksm_write_sysfs(KSM_FP("run"), 2) ||
+	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), 0) ||
+	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), 1) ||
+	    ksm_write_sysfs(KSM_FP("pages_to_scan"), page_count))
+		return KSFT_FAIL;
+
+	ret = check_ksm_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count, ksm_scan_limit_sec,
+			      page_size);
+
+	if (ksm_restore(&ksm_sysfs_old)) {
+		printf("Cannot restore default tunables\n");
+		return KSFT_FAIL;
+	}
+
+	return ret;
+}
diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index d09a6b71f1e9..97b6f712134d 100755
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -377,6 +377,22 @@  else
 	exitcode=1
 fi
 
+echo "-------------------------------------------------------"
+echo "running KSM MADV_MERGEABLE test with 10 identical pages"
+echo "-------------------------------------------------------"
+./ksm_tests -p 10
+ret_val=$?
+
+if [ $ret_val -eq 0 ]; then
+	echo "[PASS]"
+elif [ $ret_val -eq $ksft_skip ]; then
+	 echo "[SKIP]"
+	 exitcode=$ksft_skip
+else
+	echo "[FAIL]"
+	exitcode=1
+fi
+
 exit $exitcode
 
 exit $exitcode