[...]
+static void test_unmerge_zero_pages(void)
+{
+ const unsigned int size = 2 * MiB;
+ char *map;
+ unsigned long pages_expected;
+
+ ksft_print_msg("[RUN] %s\n", __func__);
+
+ if (ksm_zero_pages_fd < 0) {
+ ksft_test_result_skip("open(\"/sys/kernel/mm/ksm/ksm_zero_pages\") 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;
+ }
I realize that this test will fail if there is any other process in the system that has KSM
enabled with a suitable page filled with zeroes ... maybe instead of checking the global
KSM zeropages, check the per-mm ones instead? That should be better.
+
+ /* Mmap zero pages */
Maybe better:
/* Let KSM deduplicate zero pages. */
+ map = mmap_and_merge_range(0x00, size, false);
+ if (map == MAP_FAILED)
+ return;
+
+ /* Check if ksm_zero_pages can be update correctly after merging */
s/can be updated/is updated/
+ pages_expected = size / pagesize;
+ if (pages_expected != get_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 can be update correctly after unmerging */
+ pages_expected /= 2;
+ if (pages_expected != get_ksm_zero_pages()) {
+ ksft_test_result_fail("'ksm_zero_pages' updated after unmerging\n");
+ goto unmap;
+ }
You could do something like the following on top (I recall you had some kind of COW
tests previously, this should be a simplified version of it):
diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index ea060c683c80..160675a4e3d2 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -182,6 +182,7 @@ static void test_unmerge(void)
static void test_unmerge_zero_pages(void)
{
const unsigned int size = 2 * MiB;
+ unsigned int offs;
char *map;
unsigned long pages_expected;
@@ -225,8 +226,18 @@ static void test_unmerge_zero_pages(void)
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;
+
+ /* We should have no zeropages remaining. */
+ if (get_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 / 2),
+ ksft_test_result(!range_maps_duplicates(map, size),
"KSM zero pages were unmerged\n");
unmap:
munmap(map, size);
--
2.40.1
You could also test manual discard (MADV_DONTNEED) and munmap(). Just a thought about which
tests to add eventually later.
--
Thanks,
David / dhildenb
