On 13.04.23 15:07, David Hildenbrand wrote:

On 12.04.23 05:16, Stefan Roesch wrote:

...

This adds three new tests to the selftests for KSM. These tests use the new prctl API's to enable and disable KSM.

1. add new prctl flags to prctl header file in tools dir

   This adds the new prctl flags to the include file prct.h in the tools directory. This makes sure they are available for testing.

2. add KSM prctl merge test

   This adds the -t option to the ksm_tests program. The -t flag allows to specify if it should use madvise or prctl ksm merging.

3. add KSM get merge type test

   This adds the -G flag to the ksm_tests program to query the KSM status with prctl after KSM has been enabled with prctl.

4. add KSM fork test

   Add fork test to verify that the MMF_VM_MERGE_ANY flag is inherited by the child process.

5. add two functions for debugging merge outcome

   This adds two functions to report the metrics in /proc/self/ksm_stat and /sys/kernel/debug/mm/ksm.

The debugging can be enabled with the following command line: make -C tools/testing/selftests TARGETS="mm" --keep-going \ EXTRA_CFLAGS=-DDEBUG=1

Would it make sense to instead have a "-D" (if still unused) runtime options to print this data? Dead code that's not compiled is a bit unfortunate as it can easily bit-rot.

This patch essentially does two things

1. Add the option to run all tests/benchmarks with the PRCTL instead of

MADVISE

2. Add some functional KSM tests for the new PRCTL (fork, enabling

works, disabling works).

The latter should rather go into ksm_functional_tests().

"tools/testing/selftests/mm/ksm_functional_tests.c" is what I wanted to say.

David Hildenbrand david@redhat.com writes:

On 12.04.23 05:16, Stefan Roesch wrote:

...

This adds three new tests to the selftests for KSM. These tests use the new prctl API's to enable and disable KSM.

1. add new prctl flags to prctl header file in tools dir This adds the new prctl flags to the include file prct.h in the tools directory. This makes sure they are available for testing.
2. add KSM prctl merge test This adds the -t option to the ksm_tests program. The -t flag allows to specify if it should use madvise or prctl ksm merging.
3. add KSM get merge type test This adds the -G flag to the ksm_tests program to query the KSM status with prctl after KSM has been enabled with prctl.
4. add KSM fork test Add fork test to verify that the MMF_VM_MERGE_ANY flag is inherited by the child process.
5. add two functions for debugging merge outcome This adds two functions to report the metrics in /proc/self/ksm_stat and /sys/kernel/debug/mm/ksm.

The debugging can be enabled with the following command line: make -C tools/testing/selftests TARGETS="mm" --keep-going \ EXTRA_CFLAGS=-DDEBUG=1

Would it make sense to instead have a "-D" (if still unused) runtime options to print this data? Dead code that's not compiled is a bit unfortunate as it can easily bit-rot.

In the next version I'll add -d option. I'll add a global debug variable for this. Otherwise we would need to pass down the debug option several levels.

This patch essentially does two things

1. Add the option to run all tests/benchmarks with the PRCTL instead of MADVISE

2. Add some functional KSM tests for the new PRCTL (fork, enabling works,

disabling works).

The latter should rather go into ksm_functional_tests().

[...]

...

-static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_size) +/* Verify that prctl ksm flag is inherited. */ +static int check_ksm_fork(void) +{

• int rc = KSFT_FAIL;
• pid_t child_pid;
• if (prctl(PR_SET_MEMORY_MERGE, 1)) {

• perror("prctl");
  

• return KSFT_FAIL;
  

• }
• child_pid = fork();
• if (child_pid == 0) {

• int is_on = prctl(PR_GET_MEMORY_MERGE, 0);
  

• if (!is_on)
  

• 	exit(KSFT_FAIL);
  

• exit(KSFT_PASS);
  

• }
• if (child_pid < 0)

• goto out;
  

• if (waitpid(child_pid, &rc, 0) < 0)

• rc = KSFT_FAIL;
  

• if (prctl(PR_SET_MEMORY_MERGE, 0)) {

• perror("prctl");
  

• rc = KSFT_FAIL;
  

• }

+out:

• if (rc == KSFT_PASS)

• printf("OK\n");
  

• else

• printf("Not OK\n");
  

• return rc;

+}

+static int check_ksm_get_merge_type(void) +{

• if (prctl(PR_SET_MEMORY_MERGE, 1)) {

• perror("prctl set");
  

• return 1;
  

• }
• int is_on = prctl(PR_GET_MEMORY_MERGE, 0);
• if (prctl(PR_SET_MEMORY_MERGE, 0)) {

• perror("prctl set");
  

• return 1;
  

• }
• int is_off = prctl(PR_GET_MEMORY_MERGE, 0);
• if (is_on && is_off) {

• printf("OK\n");
  

• return KSFT_PASS;
  

• }
• printf("Not OK\n");
• return KSFT_FAIL;

+}

Yes, these two are better located in ksm_functional_tests() to just run them both automatically when the test is executed.

I moved the check_ksm_get_merge_type() and check_ksm_fork() to the ksm_functional_test executable. The change will be in the next version.