Re: [Qemu-devel] [PATCH v3 3/3] tests/migration: Add a test for auto converge

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Yury Kotov (yury-kotov@yandex-team.ru) wrote:
> Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>

This looks OK to me, but have you tried it on a really really overloaded
host?
I worry that you might skip some of the percentage steps or not hit the
bandwidth on the small overloaded VMs we get in CI.

Dave

> ---
>  tests/migration-test.c | 119 +++++++++++++++++++++++++++++++++++++----
>  1 file changed, 108 insertions(+), 11 deletions(-)
> 
> diff --git a/tests/migration-test.c b/tests/migration-test.c
> index a4feb9545d..bb69517fc8 100644
> --- a/tests/migration-test.c
> +++ b/tests/migration-test.c
> @@ -241,6 +241,17 @@ static int64_t read_ram_property_int(QTestState *who, const char *property)
>      return result;
>  }
>  
> +static int64_t read_migrate_property_int(QTestState *who, const char *property)
> +{
> +    QDict *rsp_return;
> +    int64_t result;
> +
> +    rsp_return = migrate_query(who);
> +    result = qdict_get_try_int(rsp_return, property, 0);
> +    qobject_unref(rsp_return);
> +    return result;
> +}
> +
>  static uint64_t get_migration_pass(QTestState *who)
>  {
>      return read_ram_property_int(who, "dirty-sync-count");
> @@ -255,20 +266,22 @@ static void read_blocktime(QTestState *who)
>      qobject_unref(rsp_return);
>  }
>  
> +static bool check_migration_status(QTestState *who, const char *status)
> +{
> +    bool completed;
> +    char *current_status;
> +
> +    current_status = migrate_query_status(who);
> +    completed = strcmp(current_status, status) == 0;
> +    g_assert_cmpstr(current_status, !=, "failed");
> +    g_free(current_status);
> +    return completed;
> +}
> +
>  static void wait_for_migration_status(QTestState *who,
>                                        const char *goal)
>  {
> -    while (true) {
> -        bool completed;
> -        char *status;
> -
> -        status = migrate_query_status(who);
> -        completed = strcmp(status, goal) == 0;
> -        g_assert_cmpstr(status, !=,  "failed");
> -        g_free(status);
> -        if (completed) {
> -            return;
> -        }
> +    while (!check_migration_status(who, goal)) {
>          usleep(1000);
>      }
>  }
> @@ -1121,6 +1134,89 @@ static void test_migrate_fd_proto(void)
>      test_migrate_end(from, to, true);
>  }
>  
> +static void test_migrate_auto_converge(void)
> +{
> +    char *uri = g_strdup_printf("unix:%s/migsocket", tmpfs);
> +    QTestState *from, *to;
> +    int i;
> +    int64_t remaining, downtime;
> +
> +    /*
> +     * We want the test to be fast enough, but stable.
> +     * Throttle percentages are chosen to cover all cases (init, increment, max)
> +     */
> +    static const int64_t expected_pcts[] = { 0, 1, 51, 98 };
> +    const int64_t max_bandwidth = 200000000; /* ~200Mb/s */
> +    const int64_t downtime_limit = 50; /* 50ms */
> +    /*
> +     * We migrate through unix-socket (> 500Mb/s).
> +     * Thus, expected migration speed ~= bandwidth limit (< 500Mb/s).
> +     * So, we can predict expected_threshold
> +     */
> +    const int64_t expected_threshold = max_bandwidth * downtime_limit / 1000;
> +
> +    if (test_migrate_start(&from, &to, uri, false, false)) {
> +        return;
> +    }
> +
> +    migrate_set_capability(from, "auto-converge", true);
> +    migrate_set_parameter_int(from, "cpu-throttle-initial", expected_pcts[1]);
> +    migrate_set_parameter_int(from, "cpu-throttle-increment",
> +                              expected_pcts[2] - expected_pcts[1]);
> +    migrate_set_parameter_int(from, "max-cpu-throttle", expected_pcts[3]);
> +
> +    migrate_set_parameter_int(from, "max-bandwidth", max_bandwidth);
> +    migrate_set_parameter_int(from, "downtime-limit", downtime_limit);
> +
> +    /* To check remaining size after precopy */
> +    migrate_set_capability(from, "pause-before-switchover", true);
> +
> +    /* Wait for the first serial output from the source */
> +    wait_for_serial("src_serial");
> +
> +    migrate(from, uri, "{}");
> +
> +    for (i = 0; i < ARRAY_SIZE(expected_pcts); i++) {
> +        int64_t pct;
> +        pct = read_migrate_property_int(from, "cpu-throttle-percentage");
> +        g_assert_cmpint(pct, ==, expected_pcts[i]);
> +        while (pct == expected_pcts[i] && !got_stop) {
> +            usleep(1000);
> +            pct = read_migrate_property_int(from, "cpu-throttle-percentage");
> +        }
> +        /* We break out of this loop only in paused state */
> +        if (got_stop || i + 1 == ARRAY_SIZE(expected_pcts)) {
> +            /* Check unexpected throttle percentage change */
> +            g_assert_true(got_stop);
> +            /* Check unexpected converge */
> +            g_assert_cmpint(i + 1, ==, ARRAY_SIZE(expected_pcts));
> +            g_assert_true(check_migration_status(from, "pre-switchover"));
> +        }
> +    }
> +
> +    remaining = read_ram_property_int(from, "remaining");
> +    g_assert_cmpint(remaining, <, expected_threshold);
> +
> +    wait_command(from, "{ 'execute': 'migrate-continue' , 'arguments':"
> +                       "  { 'state': 'pre-switchover' } }");
> +
> +    qtest_qmp_eventwait(to, "RESUME");
> +
> +    wait_for_serial("dest_serial");
> +    wait_for_migration_complete(from);
> +
> +    downtime = read_migrate_property_int(from, "downtime");
> +    /*
> +     * Actual downtime may be greater than downtime limit,
> +     * but the difference should be small enough (~20ms)
> +     */
> +    g_assert_cmpint(downtime, <, downtime_limit + 20);
> +
> +    g_free(uri);
> +
> +    test_migrate_end(from, to, true);
> +}
> +
>  int main(int argc, char **argv)
>  {
>      char template[] = "/tmp/migration-test-XXXXXX";
> @@ -1176,6 +1272,7 @@ int main(int argc, char **argv)
>      /* qtest_add_func("/migration/ignore_shared", test_ignore_shared); */
>      qtest_add_func("/migration/xbzrle/unix", test_xbzrle_unix);
>      qtest_add_func("/migration/fd_proto", test_migrate_fd_proto);
> +    qtest_add_func("/migration/auto_converge", test_migrate_auto_converge);
>  
>      ret = g_test_run();
>  
> -- 
> 2.22.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK