[PATCH v3 1/2] selftests: vm: add KSM merging time test

[Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>]

Add ksm_merge_time() function to determine speed and time needed for
merging. The total spent time is shown in seconds while speed is
in MiB/s. User must specify the size of duplicated memory area (in MiB)
before running the test.

The test is run as follows: ./ksm_tests -P -s 100
The output:
	Total size:    100 MiB
	Total time:    0.201106786 s
	Average speed:  497.248 MiB/s

Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
---
v2 -> v3:
 - no changes

v1 -> v2:
 As suggested by Pavel,
 - replace MB with MiB
 - measure speed more accurately

Pavel's comments: https://lkml.org/lkml/2021/8/3/1362 

 tools/testing/selftests/vm/ksm_tests.c | 74 ++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index cdeb4a028538..432dfe615e50 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -7,6 +7,7 @@
 #include <numa.h>
 
 #include "../kselftest.h"
+#include "../../../../include/vdso/time64.h"
 
 #define KSM_SYSFS_PATH "/sys/kernel/mm/ksm/"
 #define KSM_FP(s) (KSM_SYSFS_PATH s)
@@ -15,6 +16,7 @@
 #define KSM_PROT_STR_DEFAULT "rw"
 #define KSM_USE_ZERO_PAGES_DEFAULT false
 #define KSM_MERGE_ACROSS_NODES_DEFAULT true
+#define MB (1ul << 20)
 
 struct ksm_sysfs {
 	unsigned long max_page_sharing;
@@ -30,7 +32,8 @@ enum ksm_test_name {
 	CHECK_KSM_MERGE,
 	CHECK_KSM_UNMERGE,
 	CHECK_KSM_ZERO_PAGE_MERGE,
-	CHECK_KSM_NUMA_MERGE
+	CHECK_KSM_NUMA_MERGE,
+	KSM_MERGE_TIME
 };
 
 static int ksm_write_sysfs(const char *file_path, unsigned long val)
@@ -86,13 +89,16 @@ static int str_to_prot(char *prot_str)
 static void print_help(void)
 {
 	printf("usage: ksm_tests [-h] <test type> [-a prot] [-p page_count] [-l timeout]\n"
-	       "[-z use_zero_pages] [-m merge_across_nodes]\n");
+	       "[-z use_zero_pages] [-m merge_across_nodes] [-s size]\n");
 
 	printf("Supported <test type>:\n"
 	       " -M (page merging)\n"
 	       " -Z (zero pages merging)\n"
 	       " -N (merging of pages in different NUMA nodes)\n"
-	       " -U (page unmerging)\n\n");
+	       " -U (page unmerging)\n"
+	       " -P evaluate merging time and speed.\n"
+	       "    For this test, the size of duplicated memory area (in MiB)\n"
+	       "    must be provided using -s option\n\n");
 
 	printf(" -a: specify the access protections of pages.\n"
 	       "     <prot> must be of the form [rwx].\n"
@@ -105,6 +111,7 @@ static void print_help(void)
 	       "     Default: %d\n", KSM_USE_ZERO_PAGES_DEFAULT);
 	printf(" -m: change merge_across_nodes tunable\n"
 	       "     Default: %d\n", KSM_MERGE_ACROSS_NODES_DEFAULT);
+	printf(" -s: the size of duplicated memory area (in MiB)\n");
 
 	exit(0);
 }
@@ -407,6 +414,47 @@ static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_a
 	return KSFT_FAIL;
 }
 
+static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size)
+{
+	void *map_ptr;
+	struct timespec start_time, end_time;
+	unsigned long scan_time_ns;
+
+	map_size *= MB;
+
+	map_ptr = allocate_memory(NULL, prot, mapping, '*', map_size);
+	if (!map_ptr)
+		return KSFT_FAIL;
+
+	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
+		perror("clock_gettime");
+		goto err_out;
+	}
+	if (ksm_merge_pages(map_ptr, map_size, start_time, timeout))
+		goto err_out;
+	if (clock_gettime(CLOCK_MONOTONIC_RAW, &end_time)) {
+		perror("clock_gettime");
+		goto err_out;
+	}
+
+	scan_time_ns = (end_time.tv_sec - start_time.tv_sec) * NSEC_PER_SEC +
+		       (end_time.tv_nsec - start_time.tv_nsec);
+
+	printf("Total size:    %lu MiB\n", map_size / MB);
+	printf("Total time:    %ld.%09ld s\n", scan_time_ns / NSEC_PER_SEC,
+	       scan_time_ns % NSEC_PER_SEC);
+	printf("Average speed:  %.3f MiB/s\n", (map_size / MB) /
+					       ((double)scan_time_ns / NSEC_PER_SEC));
+
+	munmap(map_ptr, map_size);
+	return KSFT_PASS;
+
+err_out:
+	printf("Not OK\n");
+	munmap(map_ptr, map_size);
+	return KSFT_FAIL;
+}
+
 int main(int argc, char *argv[])
 {
 	int ret, opt;
@@ -418,8 +466,9 @@ int main(int argc, char *argv[])
 	int test_name = CHECK_KSM_MERGE;
 	bool use_zero_pages = KSM_USE_ZERO_PAGES_DEFAULT;
 	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
+	long size_MB = 0;
 
-	while ((opt = getopt(argc, argv, "ha:p:l:z:m:MUZN")) != -1) {
+	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:MUZNP")) != -1) {
 		switch (opt) {
 		case 'a':
 			prot = str_to_prot(optarg);
@@ -453,6 +502,12 @@ int main(int argc, char *argv[])
 			else
 				merge_across_nodes = 1;
 			break;
+		case 's':
+			size_MB = atoi(optarg);
+			if (size_MB <= 0) {
+				printf("Size must be greater than 0\n");
+				return KSFT_FAIL;
+			}
 		case 'M':
 			break;
 		case 'U':
@@ -464,6 +519,9 @@ int main(int argc, char *argv[])
 		case 'N':
 			test_name = CHECK_KSM_NUMA_MERGE;
 			break;
+		case 'P':
+			test_name = KSM_MERGE_TIME;
+			break;
 		default:
 			return KSFT_FAIL;
 		}
@@ -505,6 +563,14 @@ int main(int argc, char *argv[])
 		ret = check_ksm_numa_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
 					   merge_across_nodes, page_size);
 		break;
+	case KSM_MERGE_TIME:
+		if (size_MB == 0) {
+			printf("Option '-s' is required.\n");
+			return KSFT_FAIL;
+		}
+		ret = ksm_merge_time(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
+				     size_MB);
+		break;
 	}
 
 	if (ksm_restore(&ksm_sysfs_old)) {
-- 
2.25.1