Re: [PATCH v2 2/4] selftests: vm: add KSM unmerge test

[Tyler Hicks <tyhicks@linux.microsoft.com>]

On 2021-07-14 14:56:09, Zhansaya Bagdauletkyzy wrote:
> Add check_ksm_unmerge() function to verify that KSM is properly
> unmerging shared pages. For this, two duplicate pages are merged first
> and then their contents are modified. Since they are not identical
> anymore, the pages must be unmerged and the number of merged pages has
> to be 0. The test is run as follows: ./ksm_tests -U
> 
> Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

Tyler

> ---
>  tools/testing/selftests/vm/ksm_tests.c    | 72 +++++++++++++++++++++--
>  tools/testing/selftests/vm/run_vmtests.sh | 18 +++++-
>  2 files changed, 85 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
> index d74d5aa34b16..80302bb8f64c 100644
> --- a/tools/testing/selftests/vm/ksm_tests.c
> +++ b/tools/testing/selftests/vm/ksm_tests.c
> @@ -23,6 +23,11 @@ struct ksm_sysfs {
>  	unsigned long use_zero_pages;
>  };
>  
> +enum ksm_test_name {
> +	CHECK_KSM_MERGE,
> +	CHECK_KSM_UNMERGE
> +};
> +
>  static int ksm_write_sysfs(const char *file_path, unsigned long val)
>  {
>  	FILE *f = fopen(file_path, "w");
> @@ -75,7 +80,12 @@ static int str_to_prot(char *prot_str)
>  
>  static void print_help(void)
>  {
> -	printf("usage: ksm_tests [-h] [-a prot] [-p page_count] [-l timeout]\n");
> +	printf("usage: ksm_tests [-h] <test type> [-a prot] [-p page_count] [-l timeout]\n");
> +
> +	printf("Supported <test type>:\n"
> +	       " -M (page merging)\n"
> +	       " -U (page unmerging)\n\n");
> +
>  	printf(" -a: specify the access protections of pages.\n"
>  	       "     <prot> must be of the form [rwx].\n"
>  	       "     Default: %s\n", KSM_PROT_STR_DEFAULT);
> @@ -239,6 +249,46 @@ static int check_ksm_merge(int mapping, int prot, long page_count, int timeout,
>  	return KSFT_FAIL;
>  }
>  
> +static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_size)
> +{
> +	void *map_ptr;
> +	struct timespec start_time;
> +	int page_count = 2;
> +
> +	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
> +		perror("clock_gettime");
> +		return KSFT_FAIL;
> +	}
> +
> +	/* fill pages with the same data and merge them */
> +	map_ptr = allocate_memory(NULL, prot, mapping, '*', page_size * page_count);
> +	if (!map_ptr)
> +		return KSFT_FAIL;
> +
> +	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
> +		goto err_out;
> +
> +	/* change 1 byte in each of the 2 pages -- KSM must automatically unmerge them */
> +	memset(map_ptr, '-', 1);
> +	memset(map_ptr + page_size, '+', 1);
> +
> +	/* get at least 1 scan, so KSM can detect that the pages were modified */
> +	if (ksm_do_scan(1, start_time, timeout))
> +		goto err_out;
> +
> +	/* check that unmerging was successful and 0 pages are currently merged */
> +	if (assert_ksm_pages_count(0)) {
> +		printf("OK\n");
> +		munmap(map_ptr, page_size * page_count);
> +		return KSFT_PASS;
> +	}
> +
> +err_out:
> +	printf("Not OK\n");
> +	munmap(map_ptr, page_size * page_count);
> +	return KSFT_FAIL;
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	int ret, opt;
> @@ -247,8 +297,9 @@ int main(int argc, char *argv[])
>  	long page_count = KSM_PAGE_COUNT_DEFAULT;
>  	size_t page_size = sysconf(_SC_PAGESIZE);
>  	struct ksm_sysfs ksm_sysfs_old;
> +	int test_name = CHECK_KSM_MERGE;
>  
> -	while ((opt = getopt(argc, argv, "ha:p:l:")) != -1) {
> +	while ((opt = getopt(argc, argv, "ha:p:l:MU")) != -1) {
>  		switch (opt) {
>  		case 'a':
>  			prot = str_to_prot(optarg);
> @@ -270,6 +321,11 @@ int main(int argc, char *argv[])
>  		case 'h':
>  			print_help();
>  			break;
> +		case 'M':
> +			break;
> +		case 'U':
> +			test_name = CHECK_KSM_UNMERGE;
> +			break;
>  		default:
>  			return KSFT_FAIL;
>  		}
> @@ -294,8 +350,16 @@ int main(int argc, char *argv[])
>  	    ksm_write_sysfs(KSM_FP("pages_to_scan"), page_count))
>  		return KSFT_FAIL;
>  
> -	ret = check_ksm_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count, ksm_scan_limit_sec,
> -			      page_size);
> +	switch (test_name) {
> +	case CHECK_KSM_MERGE:
> +		ret = check_ksm_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
> +				      ksm_scan_limit_sec, page_size);
> +		break;
> +	case CHECK_KSM_UNMERGE:
> +		ret = check_ksm_unmerge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
> +					page_size);
> +		break;
> +	}
>  
>  	if (ksm_restore(&ksm_sysfs_old)) {
>  		printf("Cannot restore default tunables\n");
> diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
> index 97b6f712134d..3a23c6b47da2 100755
> --- a/tools/testing/selftests/vm/run_vmtests.sh
> +++ b/tools/testing/selftests/vm/run_vmtests.sh
> @@ -380,7 +380,23 @@ fi
>  echo "-------------------------------------------------------"
>  echo "running KSM MADV_MERGEABLE test with 10 identical pages"
>  echo "-------------------------------------------------------"
> -./ksm_tests -p 10
> +./ksm_tests -M -p 10
> +ret_val=$?
> +
> +if [ $ret_val -eq 0 ]; then
> +	echo "[PASS]"
> +elif [ $ret_val -eq $ksft_skip ]; then
> +	 echo "[SKIP]"
> +	 exitcode=$ksft_skip
> +else
> +	echo "[FAIL]"
> +	exitcode=1
> +fi
> +
> +echo "------------------------"
> +echo "running KSM unmerge test"
> +echo "------------------------"
> +./ksm_tests -U
>  ret_val=$?
>  
>  if [ $ret_val -eq 0 ]; then
> -- 
> 2.25.1
>