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Date: Thu, 25 May 2023 13:54:10 +0800
From: Yang Yang <yang.yang29@....com.cn>
To: akpm@...ux-foundation.org, david@...hat.com
Cc: yang.yang29@....com.cn, imbrenda@...ux.ibm.com,
jiang.xuexin@....com.cn, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, ran.xiaokai@....com.cn, xu.xin.sc@...il.com,
xu.xin16@....com.cn
Subject: [PATCH v10 5/5] selftest: add a testcase of ksm zero pages
From: xu xin <xu.xin16@....com.cn>
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.
Signed-off-by: xu xin <xu.xin16@....com.cn>
Reviewed-by: Xiaokai Ran <ran.xiaokai@....com.cn>
Reviewed-by: Yang Yang <yang.yang29@....com.cn>
Cc: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Xuexin Jiang <jiang.xuexin@....com.cn>
---
tools/testing/selftests/mm/ksm_functional_tests.c | 98 ++++++++++++++++++++++-
1 file changed, 97 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..0de9d33cd565 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 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();
--
2.15.2
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