From: xu xin <[email protected]>
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 three 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;
(3) whether ksm zero pages are really unmerged.
Signed-off-by: xu xin <[email protected]>
Cc: Claudio Imbrenda <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Xuexin Jiang <[email protected]>
Reviewed-by: Xiaokai Ran <[email protected]>
Reviewed-by: Yang Yang <[email protected]>
---
tools/testing/selftests/mm/ksm_functional_tests.c | 78 ++++++++++++++++++++++-
1 file changed, 77 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index 26853badae70..ea060c683c80 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -29,6 +29,8 @@
static int ksm_fd;
static int ksm_full_scans_fd;
+static int ksm_zero_pages_fd;
+static int ksm_use_zero_pages_fd;
static int pagemap_fd;
static size_t pagesize;
@@ -59,6 +61,24 @@ static bool range_maps_duplicates(char *addr, unsigned long size)
return false;
}
+static long get_ksm_zero_pages(void)
+{
+ char buf[20];
+ ssize_t read_size;
+ unsigned long ksm_zero_pages;
+
+ if (!ksm_zero_pages_fd)
+ return 0;
+
+ read_size = pread(ksm_zero_pages_fd, buf, sizeof(buf) - 1, 0);
+ if (read_size < 0)
+ return -errno;
+ buf[read_size] = 0;
+ ksm_zero_pages = strtol(buf, NULL, 10);
+
+ return ksm_zero_pages;
+}
+
static long ksm_get_full_scans(void)
{
char buf[10];
@@ -159,6 +179,59 @@ static void test_unmerge(void)
munmap(map, size);
}
+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;
+ }
+
+ /* Mmap 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 */
+ 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;
+ }
+
+ /* Check if ksm zero pages are really unmerged */
+ ksft_test_result(!range_maps_duplicates(map, size / 2),
+ "KSM zero pages were unmerged\n");
+unmap:
+ munmap(map, size);
+}
+
static void test_unmerge_discarded(void)
{
const unsigned int size = 2 * MiB;
@@ -358,7 +431,7 @@ 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 +452,11 @@ 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");
+ ksm_zero_pages_fd = open("/sys/kernel/mm/ksm/ksm_zero_pages", 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();
--
2.15.2
[...]
> +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
>> + 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
Emmm, yes. It makes sense. I'll do it per-mm in next-version.
>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):
>
Ok. Thank you.
>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);