在 2024/3/22 19:43, David Hildenbrand 写道:
On 22.03.24 07:09, Jinjiang Tu wrote:
This extends test_prctl_fork() and test_prctl_fork_exec() to make sure
that deduplication really happens, instead of only test the
MMF_VM_MERGE_ANY flag is set.
Signed-off-by: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
---
.../selftests/mm/ksm_functional_tests.c | 79 +++++++++++++++++--
1 file changed, 73 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c
b/tools/testing/selftests/mm/ksm_functional_tests.c
index d615767e396b..01999aab2e37 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -146,6 +146,54 @@ static int ksm_unmerge(void)
return 0;
}
+static int child_test_merge(void)
+{
+ const unsigned int size = 2 * MiB;
+ char *map;
+ int ret = -1;
+
+ /* Stabilize accounting by disabling KSM completely. */
+ if (ksm_unmerge()) {
+ ksft_print_msg("Disabling (unmerging) KSM failed\n");
+ return ret;
+ }
+
+ if (get_my_merging_pages() > 0) {
+ ksft_print_msg("Still pages merged\n");
+ return ret;
+ }
+
+ map = mmap(NULL, size, PROT_READ|PROT_WRITE,
+ MAP_PRIVATE|MAP_ANON, -1, 0);
+ if (map == MAP_FAILED) {
+ ksft_print_msg("mmap() failed\n");
+ return ret;
+ }
+
+ /* Don't use THP. Ignore if THP are not around on a kernel. */
+ if (madvise(map, size, MADV_NOHUGEPAGE) && errno != EINVAL) {
+ ksft_print_msg("MADV_NOHUGEPAGE failed\n");
+ goto unmap;
+ }
+
+ memset(map, 0x1c, size);
+
+ if (ksm_merge()) {
+ ksft_print_msg("Running KSM failed\n");
+ goto unmap;
+ }
+
+ if (get_my_merging_pages() <= 0) {
+ ksft_print_msg("Fail to merge\n");
+ goto unmap;
+ }
Looks like all you want is use mmap_and_merge_range(), but neither
setting the prctl nor madvise().
Two alternatives:
1) switching from "bool use_prctl" to an enum like
enum ksm_merge_mode {
KSM_MERGE_PRCTL
KSM_MERGE_MADVISE,
KSM_MERGE_NONE, /* PRCTL already set */
};
Then, you can simply use mmap_and_merge_range(0x1c, 2 * MiB,
PROT_READ|PROT_WRITE, KSM_MERGE_NONE);
I have considered this before. But, mmap_and_merge_range() calls
ksft_test_result_fail() when error occurs, ksft_test_result_fail()
prints prefixed with ksft_fail count. When mmap_and_merge_range() is
called in the child process, the ksft_fail isn't consisent with the
parent process due to the global variable ksft_fail is CoWed. As a
result, ksft_print_msg() is intended to be called in child process.
Maybe, We could introduce a macro ksm_print() to control which function
is called according to ksm_merge_mode :
#define ksm_print(mode, fmt, ...) do { \
if ((mode) == KSM_MERGE_NONE) \
ksft_print_msg(fmt, ##__VA_ARGS__);\
else \
ksft_test_result_fail(fmt, ##__VA_ARGS__);\
} while (0)
2) With "bool use_prctl", before doing the prctl(PR_SET_MEMORY_MERGE,
...), check if it is already enabled.
As we do that already in ksm_fork_exec_child(), and fail if it isn't
set, that should work.
Then, you can simply use mmap_and_merge_range(0x1c, 2 * MiB,
PROT_READ|PROT_WRITE, true);
here.
+
+ ret = 0;
+unmap:
+ munmap(map, size);
+ return ret;
+}
+
static char *mmap_and_merge_range(char val, unsigned long size, int
prot,
bool use_prctl)
{
@@ -458,7 +506,11 @@ static void test_prctl_fork(void)
child_pid = fork();
if (!child_pid) {
- exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0));
+ if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1)
+ exit(-1);
+ if (child_test_merge() != 0)
+ exit(-2);
+ exit(0);
} else if (child_pid < 0) {
ksft_test_result_fail("fork() failed\n");
return;
@@ -467,8 +519,14 @@ static void test_prctl_fork(void)
if (waitpid(child_pid, &status, 0) < 0) {
ksft_test_result_fail("waitpid() failed\n");
return;
- } else if (WEXITSTATUS(status) != 1) {
- ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result
in child\n");
+ }
+
+ status = WEXITSTATUS(status);
+ if (status != 0) {
+ if (status == -1)
+ ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE
result in child\n");
+ else
+ ksft_test_result_fail("fail to merge in child\n");
return;
}
@@ -483,7 +541,13 @@ static void test_prctl_fork(void)
static int ksm_fork_exec_child(void)
{
/* Test if KSM is enabled for the process. */
- return prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) == 1;
+ if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1)
+ return -1;
+
+ if (child_test_merge() != 0)
You can drop the "!=0". But maybe, you can just inline the call to
mmap_and_merge_range() here.
+ return -2;
+
+ return 0;
