set_var.cc, mysqld.cc, ha_innodb.h, innodb.test, innodb.result:

  Create new innodb_sync_spin_loops variable

mysql-test/r/innodb.result

@@ -1715,5 +1715,20 @@ Innodb_row_lock_time_max	0
 show status like "Innodb_row_lock_time_avg";
 Variable_name	Value
 Innodb_row_lock_time_avg	0
+show variables like "innodb_sync_spin_loops";
+Variable_name	Value
+innodb_sync_spin_loops	20
+set global innodb_sync_spin_loops=1000;
+show variables like "innodb_sync_spin_loops";
+Variable_name	Value
+innodb_sync_spin_loops	1000
+set global innodb_sync_spin_loops=0;
+show variables like "innodb_sync_spin_loops";
+Variable_name	Value
+innodb_sync_spin_loops	0
+set global innodb_sync_spin_loops=20;
+show variables like "innodb_sync_spin_loops";
+Variable_name	Value
+innodb_sync_spin_loops	20
 create table t1 (v varchar(16384)) engine=innodb;
 ERROR 42000: Column length too big for column 'v' (max = 255); use BLOB instead

mysql-test/t/innodb.test

@@ -1218,6 +1218,15 @@ show status like "Innodb_row_lock_time";
 show status like "Innodb_row_lock_time_max";
 show status like "Innodb_row_lock_time_avg";
 
+# Test for innodb_sync_spin_loops variable
+show variables like "innodb_sync_spin_loops";
+set global innodb_sync_spin_loops=1000;
+show variables like "innodb_sync_spin_loops";
+set global innodb_sync_spin_loops=0;
+show variables like "innodb_sync_spin_loops";
+set global innodb_sync_spin_loops=20;
+show variables like "innodb_sync_spin_loops";
+
 #
 # Test varchar
 #

sql/ha_innodb.h

@@ -212,6 +212,7 @@ extern "C" {
 extern ulong srv_max_buf_pool_modified_pct;
 extern ulong srv_max_purge_lag;
 extern ulong srv_auto_extend_increment;
+extern ulong srv_n_spin_wait_rounds;
 extern ulong srv_max_purge_lag;
 }
 

sql/mysqld.cc

@@ -4199,6 +4199,7 @@ enum options_mysqld
   OPT_INNODB_TABLE_LOCKS,
   OPT_INNODB_OPEN_FILES,
   OPT_INNODB_AUTOEXTEND_INCREMENT,
+  OPT_INNODB_SYNC_SPIN_LOOPS,
   OPT_BDB_CACHE_SIZE,
   OPT_BDB_LOG_BUFFER_SIZE,
   OPT_BDB_MAX_LOCK,
@@ -5044,6 +5045,11 @@ log and this option does nothing anymore.",
    "How many files at the maximum InnoDB keeps open at the same time.",
    (gptr*) &innobase_open_files, (gptr*) &innobase_open_files, 0,
    GET_LONG, REQUIRED_ARG, 300L, 10L, ~0L, 0, 1L, 0},
+  {"innodb_sync_spin_loops", OPT_INNODB_SYNC_SPIN_LOOPS,
+   "Count of spin-loop rounds in InnoDB mutexes",
+   (gptr*) &srv_n_spin_wait_rounds,
+   (gptr*) &srv_n_spin_wait_rounds,
+   0, GET_LONG, REQUIRED_ARG, 20L, 0L, ~0L, 0, 1L, 0},
 #ifdef HAVE_REPLICATION
   /*
     Disabled for the 4.1.3 release. Disabling just this paragraph of code is

sql/set_var.cc

@@ -378,6 +378,8 @@ sys_var_thd_bool	sys_innodb_table_locks("innodb_table_locks",
                                                &SV::innodb_table_locks);
 sys_var_long_ptr	sys_innodb_autoextend_increment("innodb_autoextend_increment",
 							&srv_auto_extend_increment);
+sys_var_long_ptr	sys_innodb_sync_spin_loops("innodb_sync_spin_loops",
+                                             &srv_n_spin_wait_rounds);
 #endif
 
 #ifdef HAVE_NDBCLUSTER_DB
@@ -651,6 +653,7 @@ sys_var *sys_variables[]=
   &sys_innodb_table_locks,
   &sys_innodb_max_purge_lag,
   &sys_innodb_autoextend_increment,
+  &sys_innodb_sync_spin_loops,
 #endif  
 #ifdef HAVE_NDBCLUSTER_DB
   &sys_ndb_autoincrement_prefetch_sz,
@@ -763,6 +766,7 @@ struct show_var_st init_vars[]= {
   {"innodb_mirrored_log_groups", (char*) &innobase_mirrored_log_groups, SHOW_LONG},
   {"innodb_open_files", (char*) &innobase_open_files, SHOW_LONG },
   {"innodb_thread_concurrency", (char*) &innobase_thread_concurrency, SHOW_LONG },
+  {sys_innodb_sync_spin_loops.name, (char*) &sys_innodb_sync_spin_loops, SHOW_SYS},
 #endif
   {sys_interactive_timeout.name,(char*) &sys_interactive_timeout,   SHOW_SYS},
   {sys_join_buffer_size.name,   (char*) &sys_join_buffer_size,	    SHOW_SYS},