set_var.cc, mysqld.cc, ha_innodb.h, ha_innodb.cc, srv0srv.c, srv0srv.h:

  Added innodb_commit_concurrency variable


innobase/include/srv0srv.h:
  Added innodb_commit_concurrency variable
innobase/srv/srv0srv.c:
  Added innodb_commit_concurrency variable
sql/ha_innodb.cc:
  Added innodb_commit_concurrency variable
sql/ha_innodb.h:
  Added innodb_commit_concurrency variable
sql/mysqld.cc:
  Added innodb_commit_concurrency variable
sql/set_var.cc:
  Added innodb_commit_concurrency variable

innobase/include/srv0srv.h

@@ -94,6 +94,7 @@ extern ulint	srv_max_dirty_pages_pct;
 
 extern ulint	srv_force_recovery;
 extern ulong	srv_thread_concurrency;
+extern ulong	srv_commit_concurrency;
 
 extern ulint	srv_max_n_threads;
 

innobase/srv/srv0srv.c

@@ -261,6 +261,7 @@ Value 10 should be good if there are less than 4 processors + 4 disks in the
 computer. Bigger computers need bigger values. */
 
 ulong	srv_thread_concurrency	= SRV_CONCURRENCY_THRESHOLD;
+ulong   srv_commit_concurrency  = 0;
 
 os_fast_mutex_t	srv_conc_mutex;		/* this mutex protects srv_conc data
 					structures */

sql/ha_innodb.cc

@@ -48,6 +48,10 @@ have disables the InnoDB inlining in this file. */
 pthread_mutex_t innobase_share_mutex, /* to protect innobase_open_files */
                 prepare_commit_mutex; /* to force correct commit order in
 				      binlog */
+ulong commit_threads= 0;
+pthread_mutex_t commit_threads_m;
+pthread_cond_t commit_cond;
+pthread_mutex_t commit_cond_m;
 bool innodb_inited= 0;
 
 /*-----------------------------------------------------------------*/
@@ -1367,6 +1371,9 @@ innobase_init(void)
 			 		(hash_get_key) innobase_get_key, 0, 0);
         pthread_mutex_init(&innobase_share_mutex, MY_MUTEX_INIT_FAST);
         pthread_mutex_init(&prepare_commit_mutex, MY_MUTEX_INIT_FAST);
+        pthread_mutex_init(&commit_threads_m, MY_MUTEX_INIT_FAST);
+        pthread_mutex_init(&commit_cond_m, MY_MUTEX_INIT_FAST);
+        pthread_cond_init(&commit_cond, NULL);
 	innodb_inited= 1;
 
 	/* If this is a replication slave and we needed to do a crash recovery,
@@ -1416,6 +1423,9 @@ innobase_end(void)
 						MYF(MY_ALLOW_ZERO_PTR));
                 pthread_mutex_destroy(&innobase_share_mutex);
                 pthread_mutex_destroy(&prepare_commit_mutex);
+                pthread_mutex_destroy(&commit_threads_m);
+                pthread_mutex_destroy(&commit_cond_m);
+                pthread_cond_destroy(&commit_cond);
 	}
 
   	DBUG_RETURN(err);
@@ -1542,7 +1552,9 @@ innobase_commit(
 	reserve the kernel mutex, we have to release the search system latch
 	first to obey the latching order. */
 
-	innobase_release_stat_resources(trx);
+        if (trx->has_search_latch) {
+                          trx_search_latch_release_if_reserved(trx);
+        }
         
         /* The flag trx->active_trans is set to 1 in
 
@@ -1575,16 +1587,41 @@ innobase_commit(
 
                 /* We need current binlog position for ibbackup to work.
                 Note, the position is current because of prepare_commit_mutex */
+retry:
+                if (srv_commit_concurrency > 0)
+                {
+                  pthread_mutex_lock(&commit_cond_m);
+                  commit_threads++;
+                  if (commit_threads > srv_commit_concurrency)
+                  {
+                    commit_threads--;
+                    pthread_cond_wait(&commit_cond, &commit_cond_m);
+                    pthread_mutex_unlock(&commit_cond_m);
+                    goto retry;
+                  }
+                  else
+                    pthread_mutex_unlock(&commit_cond_m);
+                }
+                
                 trx->mysql_log_file_name = mysql_bin_log.get_log_fname();
                 trx->mysql_log_offset =
                         (ib_longlong)mysql_bin_log.get_log_file()->pos_in_file;
 
 		innobase_commit_low(trx);
 
+                if (srv_commit_concurrency > 0)
+                {
+                  pthread_mutex_lock(&commit_cond_m);
+                  commit_threads--;
+                  pthread_cond_signal(&commit_cond);
+                  pthread_mutex_unlock(&commit_cond_m);
+                }
+                
                 if (trx->active_trans == 2) {
 
                         pthread_mutex_unlock(&prepare_commit_mutex);
                 }
+               
                 trx->active_trans = 0;
                
 	} else {
@@ -1606,7 +1643,11 @@ innobase_commit(
 
 	/* Tell the InnoDB server that there might be work for utility
 	threads: */
+        if (trx->declared_to_be_inside_innodb) {
+                          /* Release our possible ticket in the FIFO */
 
+                          srv_conc_force_exit_innodb(trx);
+        }
 	srv_active_wake_master_thread();
 
 	DBUG_RETURN(0);

sql/ha_innodb.h

@@ -232,6 +232,7 @@ extern ulong srv_n_spin_wait_rounds;
 extern ulong srv_n_free_tickets_to_enter;
 extern ulong srv_thread_sleep_delay;
 extern ulong srv_thread_concurrency;
+extern ulong srv_commit_concurrency;
 }
 
 extern TYPELIB innobase_lock_typelib;

sql/mysqld.cc

@@ -5314,6 +5314,10 @@ log and this option does nothing anymore.",
    "Helps in performance tuning in heavily concurrent environments.",
    (gptr*) &srv_thread_concurrency, (gptr*) &srv_thread_concurrency,
    0, GET_LONG, REQUIRED_ARG, 20, 1, 1000, 0, 1, 0},
+  {"innodb_commit_concurrency", OPT_INNODB_THREAD_CONCURRENCY,
+   "Helps in performance tuning in heavily concurrent environments.",
+   (gptr*) &srv_commit_concurrency, (gptr*) &srv_commit_concurrency,
+   0, GET_LONG, REQUIRED_ARG, 0, 0, 1000, 0, 1, 0},
   {"innodb_thread_sleep_delay", OPT_INNODB_THREAD_SLEEP_DELAY,
    "Time of innodb thread sleeping before joining InnoDB queue (usec). Value 0"
     " disable a sleep",

sql/set_var.cc

@@ -411,6 +411,8 @@ sys_var_long_ptr  sys_innodb_thread_sleep_delay("innodb_thread_sleep_delay",
                                                 &srv_thread_sleep_delay);
 sys_var_long_ptr  sys_innodb_thread_concurrency("innodb_thread_concurrency",
                                                 &srv_thread_concurrency);
+sys_var_long_ptr  sys_innodb_commit_concurrency("innodb_commit_concurrency",
+                                                &srv_commit_concurrency);
 #endif
 
 /* Condition pushdown to storage engine */
@@ -708,6 +710,7 @@ sys_var *sys_variables[]=
   &sys_innodb_concurrency_tickets,
   &sys_innodb_thread_sleep_delay,
   &sys_innodb_thread_concurrency,
+  &sys_innodb_commit_concurrency,
 #endif  
   &sys_trust_routine_creators,
   &sys_engine_condition_pushdown,
@@ -828,6 +831,7 @@ struct show_var_st init_vars[]= {
   {sys_innodb_table_locks.name, (char*) &sys_innodb_table_locks, SHOW_SYS},
   {sys_innodb_support_xa.name, (char*) &sys_innodb_support_xa, SHOW_SYS},
   {sys_innodb_thread_concurrency.name, (char*) &sys_innodb_thread_concurrency, SHOW_SYS},
+  {sys_innodb_commit_concurrency.name, (char*) &sys_innodb_commit_concurrency, SHOW_SYS},
   {sys_innodb_thread_sleep_delay.name, (char*) &sys_innodb_thread_sleep_delay, SHOW_SYS},
 #endif
   {sys_interactive_timeout.name,(char*) &sys_interactive_timeout,   SHOW_SYS},