Commit 3d0745e5 authored by xu xin's avatar xu xin Committed by Andrew Morton
Browse files

selftest: add a testcase of ksm zero pages 

Add a function test_unmerge_zero_page() to test the functionality on
unsharing and counting ksm-placed zero pages and counting of this patch
series.

test_unmerge_zero_page() actually contains four subjct test objects:
(1) whether the count of ksm zero pages can update correctly after merging;
(2) whether the count of ksm zero pages can update correctly after
    unmerging by madvise(...MADV_UNMERGEABLE);
(3) whether the count of ksm zero pages can update correctly after
	unmerging by triggering write fault.
(4) whether ksm zero pages are really unmerged.

Link: https://lkml.kernel.org/r/20230613030947.186089-1-yang.yang29@zte.com.cn


Signed-off-by: default avatarxu xin <xu.xin16@zte.com.cn>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarXiaokai Ran <ran.xiaokai@zte.com.cn>
Reviewed-by: default avatarYang Yang <yang.yang29@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 1a8e8430

tools/testing/selftests/mm/ksm_functional_tests.c

+97 −1
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 


static int ksm_fd;

static int ksm_full_scans_fd;

static int proc_self_ksm_stat_fd;

static int ksm_use_zero_pages_fd;

static int pagemap_fd;

static size_t pagesize;
@@ -59,6 +61,33 @@ 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 ksm_get_full_scans(void)

{

	char buf[10];
@@ -159,6 +188,70 @@ static void test_unmerge(void) 
	munmap(map, size);

}



static void test_unmerge_zero_pages(void)

{

	const unsigned int size = 2 * MiB;

	char *map;

	unsigned int offs;

	unsigned long pages_expected;



	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");

		return;

	}

	if (write(ksm_use_zero_pages_fd, "1", 1) != 1) {

		ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");

		return;

	}



	/* Let KSM deduplicate zero pages. */

	map = mmap_and_merge_range(0x00, size, false);

	if (map == MAP_FAILED)

		return;



	/* Check if ksm_zero_pages is updated correctly after KSM merging */

	pages_expected = size / pagesize;

	if (pages_expected != get_my_ksm_zero_pages()) {

		ksft_test_result_fail("'ksm_zero_pages' updated after merging\n");

		goto unmap;

	}



	/* Try to unmerge half of the region */

	if (madvise(map, size / 2, MADV_UNMERGEABLE)) {

		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");

		goto unmap;

	}



	/* Check if ksm_zero_pages is updated correctly after unmerging */

	pages_expected /= 2;

	if (pages_expected != get_my_ksm_zero_pages()) {

		ksft_test_result_fail("'ksm_zero_pages' updated after unmerging\n");

		goto unmap;

	}



	/* Trigger unmerging of the other half by writing to the pages. */

	for (offs = size / 2; offs < size; offs += pagesize)

		*((unsigned int *)&map[offs]) = offs;



	/* Now we should have no zeropages remaining. */

	if (get_my_ksm_zero_pages()) {

		ksft_test_result_fail("'ksm_zero_pages' updated after write fault\n");

		goto unmap;

	}



	/* Check if ksm zero pages are really unmerged */

	ksft_test_result(!range_maps_duplicates(map, size),

			"KSM zero pages were unmerged\n");

unmap:

	munmap(map, size);

}



static void test_unmerge_discarded(void)

{

	const unsigned int size = 2 * MiB;
@@ -358,7 +451,7 @@ static void test_prctl_unmerge(void) 


int main(int argc, char **argv)

{

	unsigned int tests = 5;

	unsigned int tests = 6;

	int err;



#ifdef __NR_userfaultfd
@@ -379,8 +472,11 @@ int main(int argc, char **argv) 
	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);

	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);



	test_unmerge();

	test_unmerge_zero_pages();

	test_unmerge_discarded();

#ifdef __NR_userfaultfd

	test_unmerge_uffd_wp();