MWL#116: group commit

Implement binlog_optimize_thread_scheduling option to allow benchmarking the
effect of running commit_ordered() for multiple transactions all in one
thread.

1 files changed, 62 insertions, 6 deletions

diff --git a/sql/log.cc b/sql/log.cc
index d18ded1f24e..c1e13452733 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -2510,7 +2510,8 @@ const char *MYSQL_LOG::generate_name(const char *log_name,
 MYSQL_BIN_LOG::MYSQL_BIN_LOG()
   :bytes_written(0), prepared_xids(0), file_id(1), open_count(1),
    need_start_event(TRUE),
-   group_commit_queue(0), num_commits(0), num_group_commits(0),
+   group_commit_queue(0), group_commit_queue_busy(FALSE),
+   num_commits(0), num_group_commits(0),
    is_relay_log(0),
    description_event_for_exec(0), description_event_for_queue(0)
 {
@@ -2567,6 +2568,7 @@ void MYSQL_BIN_LOG::init_pthread_objects()
   (void) my_pthread_mutex_init(&LOCK_index, MY_MUTEX_INIT_SLOW, "LOCK_index",
                                MYF_NO_DEADLOCK_DETECTION);
   (void) pthread_cond_init(&update_cond, 0);
+  (void) pthread_cond_init(&COND_queue_busy, 0);
 }
 
 
@@ -3989,6 +3991,7 @@ err:
 }
 
 
+static my_bool opt_optimize_thread_scheduling= TRUE;
 #ifndef DBUG_OFF
 static ulong opt_binlog_dbug_fsync_sleep= 0;
 #endif
@@ -4925,6 +4928,32 @@ MYSQL_BIN_LOG::write_transaction_to_binlog_events(group_commit_entry *entry)
   else
     trx_group_commit_leader(entry);
 
+  if (!opt_optimize_thread_scheduling)
+  {
+    /* For the leader, trx_group_commit_leader() already took the lock. */
+    if (orig_queue != NULL)
+      pthread_mutex_lock(&LOCK_commit_ordered);
+
+    DEBUG_SYNC(entry->thd, "commit_loop_entry_commit_ordered");
+    ++num_commits;
+    if (entry->trx_data->using_xa && !entry->error)
+      run_commit_ordered(entry->thd, entry->all);
+
+    group_commit_entry *next= entry->next;
+    if (!next)
+    {
+      group_commit_queue_busy= FALSE;
+      pthread_cond_signal(&COND_queue_busy);
+      DEBUG_SYNC(entry->thd, "commit_after_group_run_commit_ordered");
+    }
+    pthread_mutex_unlock(&LOCK_commit_ordered);
+
+    if (next)
+    {
+      next->thd->signal_wakeup_ready();
+    }
+  }
+
   if (!entry->error)
     return 0;
 
@@ -5088,6 +5117,24 @@ MYSQL_BIN_LOG::trx_group_commit_leader(group_commit_entry *leader)
   DEBUG_SYNC(leader->thd, "commit_after_release_LOCK_log");
   ++num_group_commits;
 
+  if (!opt_optimize_thread_scheduling)
+  {
+    /*
+      If we want to run commit_ordered() each in the transaction's own thread
+      context, then we need to mark the queue reserved; we need to finish all
+      threads in one group commit before the next group commit can be allowed
+      to proceed, and we cannot unlock a simple pthreads mutex in a different
+      thread from the one that locked it.
+    */
+
+    while (group_commit_queue_busy)
+      pthread_cond_wait(&COND_queue_busy, &LOCK_commit_ordered);
+    group_commit_queue_busy= TRUE;
+
+    /* Note that we return with LOCK_commit_ordered locked! */
+    DBUG_VOID_RETURN;
+  }
+
   /*
     Wakeup each participant waiting for our group commit, first calling the
     commit_ordered() methods for any transactions doing 2-phase commit.
@@ -6578,6 +6625,16 @@ static SHOW_VAR binlog_status_vars_top[]= {
   {NullS, NullS, SHOW_LONG}
 };
 
+static MYSQL_SYSVAR_BOOL(
+  optimize_thread_scheduling,
+  opt_optimize_thread_scheduling,
+  PLUGIN_VAR_READONLY,
+  "Run fast part of group commit in a single thread, to optimize kernel\n"
+  "thread scheduling",
+  NULL,
+  NULL,
+  1);
+
 #ifndef DBUG_OFF
 static MYSQL_SYSVAR_ULONG(
   dbug_fsync_sleep,
@@ -6590,13 +6647,16 @@ static MYSQL_SYSVAR_ULONG(
   0,
   ULONG_MAX,
   0);
+#endif
 
 static struct st_mysql_sys_var *binlog_sys_vars[]=
 {
+  MYSQL_SYSVAR(optimize_thread_scheduling),
+#ifndef DBUG_OFF
   MYSQL_SYSVAR(dbug_fsync_sleep),
+#endif
   NULL
 };
-#endif
 
 
 /*
@@ -6634,11 +6694,7 @@ mysql_declare_plugin(binlog)
   NULL, /* Plugin Deinit */
   0x0100 /* 1.0 */,
   binlog_status_vars_top,     /* status variables                */
-#ifndef DBUG_OFF
   binlog_sys_vars,            /* system variables                */
-#else
-  NULL,                       /* system variables                */
-#endif
   NULL                        /* config options                  */
 }
 mysql_declare_plugin_end;