On 25.03.24 03:24, Jinjiang Tu wrote:
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 :
As an alternative, convert all ksft_test_result_fail() in there into
ksft_print_msg(), and in the callers of mmap_and_merge_range(), do
something like
map = mmap_and_merge_range() ...
if (map == MAP_FAILED) {
ksft_test_result_fail("Merging memory failed");
return;
}
--
Cheers,
David / dhildenb
