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

Pavel Tatashin
2021-08-04T03:34:30Z

On Sun, Aug 1, 2021 at 11:43 AM Zhansaya Bagdauletkyzy
<zhansayabagdaulet@gmail.com> 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 MB/s. User must specify the size of duplicated memory area (in MB)
> before running the test.
>
> The test is run as follows: ./ksm_tests -P -s 100
> The output:
> Total size: 100 MB
> Total time: 0.309561 s
> Average speed: 323 MB/s
>
> Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
> ---
> tools/testing/selftests/vm/ksm_tests.c | 76 ++++++++++++++++++++++++--
> 1 file changed, 72 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
> index cdeb4a028538..91c6ff496655 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_TO_B 1000000ul

We should calculate everything in true megabytes.

#define MB (1ul << 20)

Also, print in MiB/s.

>
> 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 MB)\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 MB)\n");
>
> exit(0);
> }
> @@ -407,6 +414,49 @@ 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;
> + long scan_time_s, scan_time_ns;

Should be "unsigned long".

> + int avg_speed;
No needed, see below.

> +
> + map_size *= MB_TO_B;
> +
> + 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);

> + scan_time_s = scan_time_ns / NSEC_PER_SEC;
> + scan_time_ns %= NSEC_PER_SEC;
> + avg_speed = map_size / (scan_time_s * USEC_PER_SEC + scan_time_ns / NSEC_PER_USEC);

Please remove the above three lines, and replace with bellow suggestions:

> +
> + printf("Total size: %lu MB\n", map_size / MB_TO_B);

printf("Total size: %lu MiB\n", map_size / MB);

> + printf("Total time: %ld.%06ld s\n", scan_time_s, scan_time_ns / NSEC_PER_USEC);

printf("Total time: %ld.%09ld s\n", scan_time_ns / NSEC_PER_SEC,
scan_time_ns % NSEC_PER_SEC));

> + printf("Average speed: %d MB/s\n", avg_speed);

The following would give a much better precision:
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 +468,9 @@ 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 +504,12 @@ 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 +521,9 @@ 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 +565,14 @@ 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
>