InnoDB: Make the srv_thread_concurrency checks more consistent.

innobase/include/srv0srv.h:
  Define SRV_CONCURRENCY_THRESHOLD
innobase/srv/srv0srv.c:
  Remove srv_thread_concurrency check from srv_conc_enter_innodb()
  and srv_conc_exit_innodb(), as the check is in the (only) caller
  of these functions, in ha_innodb.cc.
  srv_conc_force_enter_innodb(), srv_conc_force_exit_innodb():
  Check for srv_thread_concurrency >= SRV_CONCURRENCY_THRESHOLD
sql/ha_innodb.cc:
  Make use of SRV_CONCURRENCY_THRESHOLD

innobase/include/srv0srv.h

@@ -182,6 +182,7 @@ extern mutex_t*	kernel_mutex_temp;/* mutex protecting the server, trx structs,
 #define kernel_mutex (*kernel_mutex_temp)
 
 #define SRV_MAX_N_IO_THREADS	100
+#define SRV_CONCURRENCY_THRESHOLD	20
 				
 /* Array of English strings describing the current state of an
 i/o handler thread */

innobase/srv/srv0srv.c

@@ -260,7 +260,7 @@ semaphore contention and convoy problems can occur withput this restriction.
 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	= 8;
+ulong	srv_thread_concurrency	= SRV_CONCURRENCY_THRESHOLD;
 
 os_fast_mutex_t	srv_conc_mutex;		/* this mutex protects srv_conc data
 					structures */
@@ -983,12 +983,6 @@ srv_conc_enter_innodb(
 	srv_conc_slot_t*	slot	  = NULL;
 	ulint			i;
 
-	if (srv_thread_concurrency >= 500) {
-		/* Disable the concurrency check */
-	
-		return;
-	}
-
 	/* If trx has 'free tickets' to enter the engine left, then use one
 	such ticket */
 
@@ -1134,7 +1128,7 @@ srv_conc_force_enter_innodb(
 	trx_t*	trx)	/* in: transaction object associated with the
 			thread */
 {
-	if (srv_thread_concurrency >= 500) {
+	if (srv_thread_concurrency >= SRV_CONCURRENCY_THRESHOLD) {
 	
 		return;
 	}
@@ -1160,7 +1154,7 @@ srv_conc_force_exit_innodb(
 {
 	srv_conc_slot_t*	slot	= NULL;
 
-	if (srv_thread_concurrency >= 500) {
+	if (srv_thread_concurrency >= SRV_CONCURRENCY_THRESHOLD) {
 	
 		return;
 	}
@@ -1212,11 +1206,6 @@ srv_conc_exit_innodb(
 	trx_t*	trx)	/* in: transaction object associated with the
 			thread */
 {
-	if (srv_thread_concurrency >= 500) {
-	
-		return;
-	}
-
 	if (trx->n_tickets_to_enter_innodb > 0) {
 		/* We will pretend the thread is still inside InnoDB though it
 		now leaves the InnoDB engine. In this way we save

sql/ha_innodb.cc

@@ -326,7 +326,7 @@ innodb_srv_conc_enter_innodb(
 /*=========================*/
 	trx_t*	trx)	/* in: transaction handle */
 {
-	if (UNIV_LIKELY(srv_thread_concurrency >= 20)) {
+	if (UNIV_LIKELY(srv_thread_concurrency >= SRV_CONCURRENCY_THRESHOLD)) {
 
 		return;
 	}
@@ -343,7 +343,7 @@ innodb_srv_conc_exit_innodb(
 /*========================*/
 	trx_t*	trx)	/* in: transaction handle */
 {
-	if (UNIV_LIKELY(srv_thread_concurrency >= 20)) {
+	if (UNIV_LIKELY(srv_thread_concurrency >= SRV_CONCURRENCY_THRESHOLD)) {
 
 		return;
 	}