selftests/vm: add test to measure MADV_UNMERGEABLE performance

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.

Link: https://lkml.kernel.org/r/20221021101141.84170-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index 0d85be2..f9eb4d6 100644 (file)
--- 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 @@ err_out:
        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);