selftests: vm: add KSM zero page merging test

Add check_ksm_zero_page_merge() function to test that empty pages are
being handled properly.  For this, several zero pages are allocated and
merged using madvise.  If use_zero_pages is enabled, the pages must be
shared with the special kernel zero pages; otherwise, they are merged as
usual duplicate pages.  The test is run as follows: ./ksm_tests -Z

Link: https://lkml.kernel.org/r/6d0caab00d4bdccf5e3791cb95cf6dfd5eb85e45.1626252248.git.zhansayabagdaulet@gmail.com
Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index 80302bb..5843526 100644 (file)
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -12,6 +12,7 @@
 #define KSM_SCAN_LIMIT_SEC_DEFAULT 120
 #define KSM_PAGE_COUNT_DEFAULT 10l
 #define KSM_PROT_STR_DEFAULT "rw"
+#define KSM_USE_ZERO_PAGES_DEFAULT false
 
 struct ksm_sysfs {
        unsigned long max_page_sharing;
@@ -25,7 +26,8 @@ struct ksm_sysfs {
 
 enum ksm_test_name {
        CHECK_KSM_MERGE,
-       CHECK_KSM_UNMERGE
+       CHECK_KSM_UNMERGE,
+       CHECK_KSM_ZERO_PAGE_MERGE
 };
 
 static int ksm_write_sysfs(const char *file_path, unsigned long val)
@@ -80,10 +82,12 @@ 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");
+       printf("usage: ksm_tests [-h] <test type> [-a prot] [-p page_count] [-l timeout]\n"
+              "[-z use_zero_pages]\n");
 
        printf("Supported <test type>:\n"
               " -M (page merging)\n"
+              " -Z (zero pages merging)\n"
               " -U (page unmerging)\n\n");
 
        printf(" -a: specify the access protections of pages.\n"
@@ -93,6 +97,8 @@ static void print_help(void)
               "     Default: %ld\n", KSM_PAGE_COUNT_DEFAULT);
        printf(" -l: limit the maximum running time (in seconds) for a test.\n"
               "     Default: %d seconds\n", KSM_SCAN_LIMIT_SEC_DEFAULT);
+       printf(" -z: change use_zero_pages tunable\n"
+              "     Default: %d\n", KSM_USE_ZERO_PAGES_DEFAULT);
 
        exit(0);
 }
@@ -289,6 +295,50 @@ err_out:
        return KSFT_FAIL;
 }
 
+static int check_ksm_zero_page_merge(int mapping, int prot, long page_count, int timeout,
+                                    bool use_zero_pages, size_t page_size)
+{
+       void *map_ptr;
+       struct timespec start_time;
+
+       if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
+               perror("clock_gettime");
+               return KSFT_FAIL;
+       }
+
+       if (ksm_write_sysfs(KSM_FP("use_zero_pages"), use_zero_pages))
+               return KSFT_FAIL;
+
+       /* fill pages with zero and try to merge them */
+       map_ptr = allocate_memory(NULL, prot, mapping, 0, page_size * page_count);
+       if (!map_ptr)
+               return KSFT_FAIL;
+
+       if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+               goto err_out;
+
+       /*
+       * verify that the right number of pages are merged:
+       * 1) if use_zero_pages is set to 1, empty pages are merged
+       *    with the kernel zero page instead of with each other;
+       * 2) if use_zero_pages is set to 0, empty pages are not treated specially
+       *    and merged as usual.
+       */
+       if (use_zero_pages && !assert_ksm_pages_count(0))
+               goto err_out;
+       else if (!use_zero_pages && !assert_ksm_pages_count(page_count))
+               goto err_out;
+
+       printf("OK\n");
+       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;
@@ -298,8 +348,9 @@ int main(int argc, char *argv[])
        size_t page_size = sysconf(_SC_PAGESIZE);
        struct ksm_sysfs ksm_sysfs_old;
        int test_name = CHECK_KSM_MERGE;
+       bool use_zero_pages = KSM_USE_ZERO_PAGES_DEFAULT;
 
-       while ((opt = getopt(argc, argv, "ha:p:l:MU")) != -1) {
+       while ((opt = getopt(argc, argv, "ha:p:l:z:MUZ")) != -1) {
                switch (opt) {
                case 'a':
                        prot = str_to_prot(optarg);
@@ -321,11 +372,20 @@ int main(int argc, char *argv[])
                case 'h':
                        print_help();
                        break;
+               case 'z':
+                       if (strcmp(optarg, "0") == 0)
+                               use_zero_pages = 0;
+                       else
+                               use_zero_pages = 1;
+                       break;
                case 'M':
                        break;
                case 'U':
                        test_name = CHECK_KSM_UNMERGE;
                        break;
+               case 'Z':
+                       test_name = CHECK_KSM_ZERO_PAGE_MERGE;
+                       break;
                default:
                        return KSFT_FAIL;
                }
@@ -359,6 +419,10 @@ int main(int argc, char *argv[])
                ret = check_ksm_unmerge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
                                        page_size);
                break;
+       case CHECK_KSM_ZERO_PAGE_MERGE:
+               ret = check_ksm_zero_page_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
+                                               ksm_scan_limit_sec, use_zero_pages, page_size);
+               break;
        }
 
        if (ksm_restore(&ksm_sysfs_old)) {

diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index 3a23c6b..9b4e444 100755 (executable)
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -409,6 +409,38 @@ else
        exitcode=1
 fi
 
+echo "----------------------------------------------------------"
+echo "running KSM test with 10 zero pages and use_zero_pages = 0"
+echo "----------------------------------------------------------"
+./ksm_tests -Z -p 10 -z 0
+ret_val=$?
+
+if [ $ret_val -eq 0 ]; then
+       echo "[PASS]"
+elif [ $ret_val -eq $ksft_skip ]; then
+        echo "[SKIP]"
+        exitcode=$ksft_skip
+else
+       echo "[FAIL]"
+       exitcode=1
+fi
+
+echo "----------------------------------------------------------"
+echo "running KSM test with 10 zero pages and use_zero_pages = 1"
+echo "----------------------------------------------------------"
+./ksm_tests -Z -p 10 -z 1
+ret_val=$?
+
+if [ $ret_val -eq 0 ]; then
+       echo "[PASS]"
+elif [ $ret_val -eq $ksft_skip ]; then
+        echo "[SKIP]"
+        exitcode=$ksft_skip
+else
+       echo "[FAIL]"
+       exitcode=1
+fi
+
 exit $exitcode
 
 exit $exitcode