On 2021-08-06 16:10:27, Zhansaya Bagdauletkyzy wrote:

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

Thanks for addressing all of Pavel's feedback. This looks good to me.

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

Tyler

---

v1 -> v2: As suggested by Pavel,

• replace MB with MiB
• measure speed more accurately

Pavel's review comments: https://lore.kernel.org/lkml/CA+CK2bBpzdWMYoJdR2EQNNCrRn+Pg1Gs2oBqLR65JW3UUn...

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 = atol(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

On 2021-08-06 16:10:29, Zhansaya Bagdauletkyzy wrote:

Since merged pages are copied every time they need to be modified, the write access time is different between shared and non-shared pages. Add ksm_cow_time() function which evaluates latency of these COW breaks. First, 4000 pages are allocated and the time, required to modify 1 byte in every other page, is measured. After this, the pages are merged into 2000 pairs and in each pair, 1 page is modified (i.e. they are decoupled) to detect COW breaks. The time needed to break COW of merged pages is then compared with performance of non-shared pages.

The test is run as follows: ./ksm_tests -C The output: Total size: 15 MiB

    Not merged pages:
    Total time:     0.001903112 s
    Average speed:  3678.186 MiB/s

    Merged pages:
    Total time:     0.006215680 s
    Average speed:  1126.184 MiB/s

Signed-off-by: Zhansaya Bagdauletkyzy zhansayabagdaulet@gmail.com

v1 -> v2: As suggested by Pavel,

• add baseline figures with non-shared pages
• instead of having all pages merged together, create pairs of duplicated pages

Pavel's review comments: https://lore.kernel.org/lkml/CA+CK2bDYZBBaU3pC369o01tCgydaJ6y91GZ0_MWONMMCaj...

tools/testing/selftests/vm/ksm_tests.c | 84 +++++++++++++++++++++++++- 1 file changed, 81 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c index 432dfe615e50..382ee6ccd13a 100644 --- a/tools/testing/selftests/vm/ksm_tests.c +++ b/tools/testing/selftests/vm/ksm_tests.c @@ -33,7 +33,8 @@ enum ksm_test_name { CHECK_KSM_UNMERGE, CHECK_KSM_ZERO_PAGE_MERGE, CHECK_KSM_NUMA_MERGE,

• KSM_MERGE_TIME

• KSM_MERGE_TIME,
• KSM_COW_TIME

}; static int ksm_write_sysfs(const char *file_path, unsigned long val) @@ -98,7 +99,8 @@ static void print_help(void) " -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");
  

•       "    must be provided using -s option\n"
  

•       " -C evaluate the time required to break COW of merged pages.\n\n");
  

printf(" -a: specify the access protections of pages.\n" " <prot> must be of the form [rwx].\n" @@ -455,6 +457,75 @@ static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size) return KSFT_FAIL; } +static int ksm_cow_time(int mapping, int prot, int timeout, size_t page_size) +{

• void *map_ptr;
• struct timespec start_time, end_time;
• unsigned long cow_time_ns;
• int page_count = 4000;

size_t is more correct.

• map_ptr = allocate_memory(NULL, prot, mapping, '*', page_size * page_count);
• if (!map_ptr)

• return KSFT_FAIL;
  

• if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {

• perror("clock_gettime");
  

• return KSFT_FAIL;
  

• }
• for (size_t i = 0; i < page_count; i = i + 2)

^ I think it is best to use the correct test here even though you're stepping by 2 and won't have any problems in practice:

i < (page_count - 1)

This should be changed in all for loops in this function.

• memset(map_ptr + page_size * i, '-', 1);
  

• if (clock_gettime(CLOCK_MONOTONIC_RAW, &end_time)) {

• perror("clock_gettime");
  

• return KSFT_FAIL;
  

• }
• cow_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\n", (page_size * page_count) / MB);
• printf("Not merged pages:\n");
• printf("Total time: %ld.%09ld s\n", cow_time_ns / NSEC_PER_SEC,

•       cow_time_ns % NSEC_PER_SEC);
  

• printf("Average speed: %.3f MiB/s\n\n", ((page_size * (page_count / 2)) / MB) /

• 			       ((double)cow_time_ns / NSEC_PER_SEC));
  

• /* Create 2000 pairs of duplicated pages */
• for (size_t i = 0; i < page_count; i = i + 2) {

• memset(map_ptr + page_size * i, '+', i + 1);
  

• memset(map_ptr + page_size * (i + 1), '+', i + 1);
  

• }

Since i is being used as the third argument to memset(), this loop only works if page_count is less than page_size. I could see someone quickly bumping page_count higher and then unknowingly getting bad test results.

Lets gain a little headroom in page_count. We are creating page_count/2 pairs of duplicate pages so we can use these memset() calls:

memset(map_ptr + page_size * i, '+', i / 2 + 1); memset(map_ptr + page_size * (i + 1), '+', i / 2 + 1);

Then add a short comment to the page_count declaration mentioning that page_count must be < (page_size / 2).

Everything else looks good to me.

Tyler

• if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))

• goto err_out;
  

• if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {

• perror("clock_gettime");
  

• goto err_out;
  

• }
• for (size_t i = 0; i < page_count; i = i + 2)

• memset(map_ptr + page_size * i, '-', 1);
  

• if (clock_gettime(CLOCK_MONOTONIC_RAW, &end_time)) {

• perror("clock_gettime");
  

• goto err_out;
  

• }
• cow_time_ns = (end_time.tv_sec - start_time.tv_sec) * NSEC_PER_SEC +

•        (end_time.tv_nsec - start_time.tv_nsec);
  

• printf("Merged pages:\n");
• printf("Total time: %ld.%09ld s\n", cow_time_ns / NSEC_PER_SEC,

•       cow_time_ns % NSEC_PER_SEC);
  

• printf("Average speed: %.3f MiB/s\n", ((page_size * (page_count / 2)) / MB) /

• 			       ((double)cow_time_ns / NSEC_PER_SEC));
  

• 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; @@ -468,7 +539,7 @@ int main(int argc, char *argv[]) bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT; long size_MB = 0;

• while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:MUZNP")) != -1) {

• while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:MUZNPC")) != -1) { switch (opt) { case 'a': prot = str_to_prot(optarg);

@@ -522,6 +593,9 @@ int main(int argc, char *argv[]) case 'P': test_name = KSM_MERGE_TIME; break;

• case 'C':
  

• 	test_name = KSM_COW_TIME;
  

• 	break;
  

  default: return KSFT_FAIL; }

@@ -571,6 +645,10 @@ int main(int argc, char *argv[]) ret = ksm_merge_time(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec, size_MB); break;

• case KSM_COW_TIME:

• ret = ksm_cow_time(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
  

• 		   page_size);
  

• break;
  

  }

if (ksm_restore(&ksm_sysfs_old)) { -- 2.25.1