[RFC 6/6] tests: Add migration dirtylimit capability test

[huangy81@chinatelecom.cn]

From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

Add migration dirtylimit capability test if kernel support
dirty ring.

Migration dirtylimit capability introduce dirtylimit capability
, two parameters: vcpu-dirtylimit-period and vcpu-dirtylimit to
implement the live migration with dirtylimit.

The test case enable the capability and set the corresponding
parameters to test migration. When migration switch to
pre-switchover phase, like the auto-converge, checking if
migration satisfy the convergence condition.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
---
 tests/qtest/migration-test.c | 89 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 40f2873..b0a53d7 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -1650,6 +1650,93 @@ static void test_vcpu_dirty_limit(void)
     dirtylimit_stop_vm(vm);
 }
 
+static void test_migrate_dirty_limit(void)
+{
+    g_autofree char *uri = g_strdup_printf("unix:%s/migsocket", tmpfs);
+    MigrateStart *args = migrate_start_new();
+    QTestState *from, *to;
+    int64_t remaining, throttle_us_per_full;
+    /*
+     * We want the test to be stable and as fast as possible.
+     * E.g., with 1Gb/s bandwith migration may pass without dirtylimit,
+     * so we need to decrease a bandwidth.
+     */
+    const int64_t dirtylimit_period = 1000, dirtylimit_value = 50;
+    const int64_t max_bandwidth = 400000000; /* ~400Mb/s */
+    const int64_t downtime_limit = 250; /* 250ms */
+    /*
+     * 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;
+
+    /* Enable dirty ring logging */
+    args->use_dirty_ring = true;
+
+    if (test_migrate_start(&from, &to, uri, &args)) {
+        return;
+    }
+
+    migrate_set_capability(from, "dirtylimit", true);
+    migrate_set_parameter_int(from, "vcpu-dirtylimit-period",
+                              dirtylimit_period);
+    migrate_set_parameter_int(from, "vcpu-dirtylimit", dirtylimit_value);
+
+    /*
+     * Set the initial parameters so that the migration could not converge
+     * without dirtylimit.
+     */
+    migrate_set_parameter_int(from, "downtime-limit", 1);
+    migrate_set_parameter_int(from, "max-bandwidth", 100000000); /* ~100Mb/s */
+
+    /* To check limit rate 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_qmp(from, uri, "{}");
+
+    /* Wait for dirtylimit begins */
+    throttle_us_per_full = 0;
+    while (throttle_us_per_full == 0) {
+        throttle_us_per_full =
+            read_migrate_property_int(from, "dirtylimit-throttle-us-per-full");
+        usleep(100);
+        g_assert_false(got_stop);
+    }
+
+    /*
+     * The dirtylimit rate should equals the return value of
+     * query-vcpu-dirty-limit if dirtylimit cap set
+     */
+    g_assert_cmpint(dirtylimit_value, ==, get_limit_rate(from));
+
+    /* Now, when we tested if dirtylimit works, let it converge */
+    migrate_set_parameter_int(from, "downtime-limit", downtime_limit);
+    migrate_set_parameter_int(from, "max-bandwidth", max_bandwidth);
+
+    /*
+     * Wait for pre-switchover status to check if migration
+     * satisfy the convergence condition
+     */
+    wait_for_migration_status(from, "pre-switchover", NULL);
+
+    remaining = read_ram_property_int(from, "remaining");
+    g_assert_cmpint(remaining, <,
+                    (expected_threshold + expected_threshold / 100));
+
+    migrate_continue(from, "pre-switchover");
+
+    qtest_qmp_eventwait(to, "RESUME");
+
+    wait_for_serial("dest_serial");
+    wait_for_migration_complete(from);
+
+    test_migrate_end(from, to, true);
+}
+
 static bool kvm_dirty_ring_supported(void)
 {
 #if defined(__linux__) && defined(HOST_X86_64)
@@ -1741,6 +1828,8 @@ int main(int argc, char **argv)
                        test_precopy_unix_dirty_ring);
         qtest_add_func("/migration/vcpu_dirty_limit",
                        test_vcpu_dirty_limit);
+        qtest_add_func("/migration/dirty_limit",
+                       test_migrate_dirty_limit);
     }
 
     ret = g_test_run();
-- 
1.8.3.1