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    Subject[PATCH v2 1/9] selftests/vm: add test to measure MADV_UNMERGEABLE performance
    Date
    Let's add a test to measure performance of KSM breaking not triggered
    via COW, but triggered by disabling KSM on an area filled with KSM pages
    via MADV_UNMERGEABLE.

    Acked-by: Peter Xu <peterx@redhat.com>
    Signed-off-by: David Hildenbrand <david@redhat.com>
    ---
    tools/testing/selftests/vm/ksm_tests.c | 76 +++++++++++++++++++++++++-
    1 file changed, 74 insertions(+), 2 deletions(-)

    diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
    index 0d85be2350fa..f9eb4d67e0dd 100644
    --- a/tools/testing/selftests/vm/ksm_tests.c
    +++ b/tools/testing/selftests/vm/ksm_tests.c
    @@ -40,6 +40,7 @@ enum ksm_test_name {
    CHECK_KSM_NUMA_MERGE,
    KSM_MERGE_TIME,
    KSM_MERGE_TIME_HUGE_PAGES,
    + KSM_UNMERGE_TIME,
    KSM_COW_TIME
    };

    @@ -108,7 +109,10 @@ static void print_help(void)
    " -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"
    - " -H evaluate merging time and speed of area allocated mostly with huge pages\n"
    + " -H evaluate merging time and speed of area allocated mostly with huge pages\n"
    + " For this test, the size of duplicated memory area (in MiB)\n"
    + " must be provided using -s option\n"
    + " -D evaluate unmerging time and speed when disabling KSM.\n"
    " For this test, the size of duplicated memory area (in MiB)\n"
    " must be provided using -s option\n"
    " -C evaluate the time required to break COW of merged pages.\n\n");
    @@ -188,6 +192,16 @@ static int ksm_merge_pages(void *addr, size_t size, struct timespec start_time,
    return 0;
    }

    +static int ksm_unmerge_pages(void *addr, size_t size,
    + struct timespec start_time, int timeout)
    +{
    + if (madvise(addr, size, MADV_UNMERGEABLE)) {
    + perror("madvise");
    + return 1;
    + }
    + return 0;
    +}
    +
    static bool assert_ksm_pages_count(long dupl_page_count)
    {
    unsigned long max_page_sharing, pages_sharing, pages_shared;
    @@ -560,6 +574,53 @@ static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size)
    return KSFT_FAIL;
    }

    +static int ksm_unmerge_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, &start_time)) {
    + perror("clock_gettime");
    + goto err_out;
    + }
    + if (ksm_unmerge_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;
    +}
    +
    static int ksm_cow_time(int mapping, int prot, int timeout, size_t page_size)
    {
    void *map_ptr;
    @@ -644,7 +705,7 @@ 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:MUZNPCH")) != -1) {
    + while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:MUZNPCHD")) != -1) {
    switch (opt) {
    case 'a':
    prot = str_to_prot(optarg);
    @@ -701,6 +762,9 @@ int main(int argc, char *argv[])
    case 'H':
    test_name = KSM_MERGE_TIME_HUGE_PAGES;
    break;
    + case 'D':
    + test_name = KSM_UNMERGE_TIME;
    + break;
    case 'C':
    test_name = KSM_COW_TIME;
    break;
    @@ -762,6 +826,14 @@ int main(int argc, char *argv[])
    ret = ksm_merge_hugepages_time(MAP_PRIVATE | MAP_ANONYMOUS, prot,
    ksm_scan_limit_sec, size_MB);
    break;
    + case KSM_UNMERGE_TIME:
    + if (size_MB == 0) {
    + printf("Option '-s' is required.\n");
    + return KSFT_FAIL;
    + }
    + ret = ksm_unmerge_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);
    --
    2.37.3
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