[v3,3/3] tests/migration: Add a test for auto converge

Commit Message

Yury Kotov July 18, 2019, 9:17 a.m. UTC

Signed-off-by: Yury Kotov <[e-mail]>
---
 tests/migration-test.c | 119 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 108 insertions(+), 11 deletions(-)

Comments

Dr. David Alan Gilbert July 22, 2019, 5:35 p.m. UTC | #1

* Yury Kotov ([e-mail]) wrote:
> Signed-off-by: Yury Kotov <[e-mail]>

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 / [e-mail] / Manchester, UK

Yury Kotov July 23, 2019, 8:54 a.m. UTC | #2

22.07.2019, 20:35, "Dr. David Alan Gilbert" <[e-mail]>:
> * Yury Kotov ([e-mail]) wrote:
>>  Signed-off-by: Yury Kotov <[e-mail]>
>
> 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.

No, I haven't tried. I saw patchew's logs and you're absolutely right - such
problem exists. Now I'm looking for a way to fix it.

>
> 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 / [e-mail] / Manchester, UK

Regards,
Yury

Dr. David Alan Gilbert July 23, 2019, 10:23 a.m. UTC | #3

* Yury Kotov ([e-mail]) wrote:
> 22.07.2019, 20:35, "Dr. David Alan Gilbert" <[e-mail]>:
> > * Yury Kotov ([e-mail]) wrote:
> >>  Signed-off-by: Yury Kotov <[e-mail]>
> >
> > 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.
> 
> No, I haven't tried. I saw patchew's logs and you're absolutely right - such
> problem exists. Now I'm looking for a way to fix it.

Yes, we've hit that type of thing before; make sure it's happy with 1
CPU that's already got 2 or 3 other things on it.

But as much as possible try and make it survive if it's really slow.

Dave

> >
> > 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 / [e-mail] / Manchester, UK
> 
> Regards,
> Yury
--
Dr. David Alan Gilbert / [e-mail] / Manchester, UK

Patch

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();