Re: [PATCH V4 07/11] tests/qtest: migration events

[Steven Sistare <steven.sistare@oracle.com>]

On 8/30/2023 1:00 PM, Peter Xu wrote:
> On Tue, Aug 29, 2023 at 11:18:02AM -0700, Steve Sistare wrote:
>> Define a state object to capture events seen by migration tests, to allow
>> more events to be captured in a subsequent patch, and simplify event
>> checking in wait_for_migration_pass.  No functional change.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> Reviewed-by: Fabiano Rosas <farosas@suse.de>
>> ---
>>  tests/qtest/migration-helpers.c | 24 +++++----------
>>  tests/qtest/migration-helpers.h |  8 +++--
>>  tests/qtest/migration-test.c    | 68 +++++++++++++++++++----------------------
>>  3 files changed, 44 insertions(+), 56 deletions(-)
>>
>> diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
>> index be00c52..b541108 100644
>> --- a/tests/qtest/migration-helpers.c
>> +++ b/tests/qtest/migration-helpers.c
>> @@ -23,26 +23,16 @@
>>   */
>>  #define MIGRATION_STATUS_WAIT_TIMEOUT 120
>>  
>> -bool migrate_watch_for_stop(QTestState *who, const char *name,
>> -                            QDict *event, void *opaque)
>> -{
>> -    bool *seen = opaque;
>> -
>> -    if (g_str_equal(name, "STOP")) {
>> -        *seen = true;
>> -        return true;
>> -    }
>> -
>> -    return false;
>> -}
>> -
>> -bool migrate_watch_for_resume(QTestState *who, const char *name,
>> +bool migrate_watch_for_events(QTestState *who, const char *name,
>>                                QDict *event, void *opaque)
>>  {
>> -    bool *seen = opaque;
>> +    QTestMigrationState *state = opaque;
>>  
>> -    if (g_str_equal(name, "RESUME")) {
>> -        *seen = true;
>> +    if (g_str_equal(name, "STOP")) {
>> +        state->stop_seen = true;
>> +        return true;
>> +    } else if (g_str_equal(name, "RESUME")) {
>> +        state->resume_seen = true;
>>          return true;
>>      }
>>  
>> diff --git a/tests/qtest/migration-helpers.h b/tests/qtest/migration-helpers.h
>> index 009e250..59fbb83 100644
>> --- a/tests/qtest/migration-helpers.h
>> +++ b/tests/qtest/migration-helpers.h
>> @@ -15,9 +15,11 @@
>>  
>>  #include "libqtest.h"
>>  
>> -bool migrate_watch_for_stop(QTestState *who, const char *name,
>> -                            QDict *event, void *opaque);
>> -bool migrate_watch_for_resume(QTestState *who, const char *name,
>> +typedef struct QTestMigrationState {
>> +    bool stop_seen, resume_seen;
>> +} QTestMigrationState;
>> +
>> +bool migrate_watch_for_events(QTestState *who, const char *name,
>>                                QDict *event, void *opaque);
>>  
>>  G_GNUC_PRINTF(3, 4)
>> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
>> index 62d3f37..526a1b7 100644
>> --- a/tests/qtest/migration-test.c
>> +++ b/tests/qtest/migration-test.c
>> @@ -43,8 +43,8 @@
>>  unsigned start_address;
>>  unsigned end_address;
>>  static bool uffd_feature_thread_id;
>> -static bool got_src_stop;
>> -static bool got_dst_resume;
>> +static QTestMigrationState src_state;
>> +static QTestMigrationState dst_state;
>>  
>>  /*
>>   * An initial 3 MB offset is used as that corresponds
>> @@ -188,6 +188,13 @@ static void wait_for_serial(const char *side)
>>      } while (true);
>>  }
>>  
>> +static void wait_for_stop(QTestState *who, QTestMigrationState *state)
>> +{
>> +    if (!state->stop_seen) {
>> +        qtest_qmp_eventwait(who, "STOP");
>> +    }
>> +}
>> +
>>  /*
>>   * It's tricky to use qemu's migration event capability with qtest,
>>   * events suddenly appearing confuse the qmp()/hmp() responses.
>> @@ -235,21 +242,19 @@ static void read_blocktime(QTestState *who)
>>      qobject_unref(rsp_return);
>>  }
>>  
>> +/*
>> + * Wait for two changes in the migration pass count, but bail if we stop.
>> + */
>>  static void wait_for_migration_pass(QTestState *who)
>>  {
>> -    uint64_t initial_pass = get_migration_pass(who);
>> -    uint64_t pass;
>> +    uint64_t pass, prev_pass = 0, changes = 0;
>>  
>> -    /* Wait for the 1st sync */
>> -    while (!got_src_stop && !initial_pass) {
>> -        usleep(1000);
>> -        initial_pass = get_migration_pass(who);
>> -    }
>> -
>> -    do {
>> +    while (changes < 2 && !src_state.stop_seen) {
>>          usleep(1000);
>>          pass = get_migration_pass(who);
>> -    } while (pass == initial_pass && !got_src_stop);
>> +        changes += (pass != prev_pass);
>> +        prev_pass = pass;
>> +    }
> 
> Here won't it start to wait for 2 iterations every time instead of 1?
> 
> Note that previously we only wait for 1 iteration as long as not the
> initial pass.  

I don't think so.  Both the old and new code require at least a transition from
pass 0 to 1, and pass 1 to 2, to return.  With the old:
  when initial_pass becomes non-zero, done with first loop
  when pass changes again, done with 2nd loop

- Steve

> And I think the change will double the counts for below..
> 
>             while (args->iterations > 1) {
>                 wait_for_migration_pass(from);
>                 args->iterations--;
>             }
> 
> The event-related changes are all fine, but maybe leave this piece as before?
> 
>>  }
>>  
>>  static void check_guests_ram(QTestState *who)
>> @@ -586,10 +591,7 @@ static void migrate_postcopy_start(QTestState *from, QTestState *to)
>>  {
>>      qtest_qmp_assert_success(from, "{ 'execute': 'migrate-start-postcopy' }");
>>  
>> -    if (!got_src_stop) {
>> -        qtest_qmp_eventwait(from, "STOP");
>> -    }
>> -
>> +    wait_for_stop(from, &src_state);
>>      qtest_qmp_eventwait(to, "RESUME");
>>  }
>>  
>> @@ -720,8 +722,9 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>>          }
>>      }
>>  
>> -    got_src_stop = false;
>> -    got_dst_resume = false;
>> +    dst_state = (QTestMigrationState) { };
>> +    src_state = (QTestMigrationState) { };
>> +
>>      bootpath = g_strdup_printf("%s/bootsect", tmpfs);
>>      if (strcmp(arch, "i386") == 0 || strcmp(arch, "x86_64") == 0) {
>>          /* the assembled x86 boot sector should be exactly one sector large */
>> @@ -801,8 +804,8 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>>      if (!args->only_target) {
>>          *from = qtest_init(cmd_source);
>>          qtest_qmp_set_event_callback(*from,
>> -                                     migrate_watch_for_stop,
>> -                                     &got_src_stop);
>> +                                     migrate_watch_for_events,
>> +                                     &src_state);
>>      }
>>  
>>      cmd_target = g_strdup_printf("-accel kvm%s -accel tcg "
>> @@ -821,8 +824,8 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>>                                   ignore_stderr);
>>      *to = qtest_init(cmd_target);
>>      qtest_qmp_set_event_callback(*to,
>> -                                 migrate_watch_for_resume,
>> -                                 &got_dst_resume);
>> +                                 migrate_watch_for_events,
>> +                                 &dst_state);
>>  
>>      /*
>>       * Remove shmem file immediately to avoid memory leak in test failed case.
>> @@ -1516,9 +1519,7 @@ static void test_precopy_common(MigrateCommon *args)
>>           */
>>          if (args->result == MIG_TEST_SUCCEED) {
>>              qtest_qmp_assert_success(from, "{ 'execute' : 'stop'}");
>> -            if (!got_src_stop) {
>> -                qtest_qmp_eventwait(from, "STOP");
>> -            }
>> +            wait_for_stop(from, &src_state);
>>              migrate_ensure_converge(from);
>>          }
>>      }
>> @@ -1560,9 +1561,8 @@ static void test_precopy_common(MigrateCommon *args)
>>               */
>>              wait_for_migration_complete(from);
>>  
>> -            if (!got_src_stop) {
>> -                qtest_qmp_eventwait(from, "STOP");
>> -            }
>> +            wait_for_stop(from, &src_state);
>> +
>>          } else {
>>              wait_for_migration_complete(from);
>>              /*
>> @@ -1575,7 +1575,7 @@ static void test_precopy_common(MigrateCommon *args)
>>              qtest_qmp_assert_success(to, "{ 'execute' : 'cont'}");
>>          }
>>  
>> -        if (!got_dst_resume) {
>> +        if (!dst_state.resume_seen) {
>>              qtest_qmp_eventwait(to, "RESUME");
>>          }
>>  
>> @@ -1696,9 +1696,7 @@ static void test_ignore_shared(void)
>>  
>>      migrate_wait_for_dirty_mem(from, to);
>>  
>> -    if (!got_src_stop) {
>> -        qtest_qmp_eventwait(from, "STOP");
>> -    }
>> +    wait_for_stop(from, &src_state);
>>  
>>      qtest_qmp_eventwait(to, "RESUME");
>>  
>> @@ -2139,7 +2137,7 @@ static void test_migrate_auto_converge(void)
>>              break;
>>          }
>>          usleep(20);
>> -        g_assert_false(got_src_stop);
>> +        g_assert_false(src_state.stop_seen);
>>      } while (true);
>>      /* The first percentage of throttling should be at least init_pct */
>>      g_assert_cmpint(percentage, >=, init_pct);
>> @@ -2481,9 +2479,7 @@ static void test_multifd_tcp_cancel(void)
>>  
>>      migrate_ensure_converge(from);
>>  
>> -    if (!got_src_stop) {
>> -        qtest_qmp_eventwait(from, "STOP");
>> -    }
>> +    wait_for_stop(from, &src_state);
>>      qtest_qmp_eventwait(to2, "RESUME");
>>  
>>      wait_for_serial("dest_serial");
>> -- 
>> 1.8.3.1
>>
>