diff -r 4dca80df8ee3 innobase/os/os0file.c
--- a/innobase/os/os0file.c	Mon Sep 08 16:40:14 2008 -0700
+++ b/innobase/os/os0file.c	Mon Sep 08 16:40:20 2008 -0700
@@ -3180,6 +3180,13 @@
 	struct aiocb*	control;
 #endif
 	ulint		i;
+	ulint		prim_segment;
+	ulint		n;
+
+	n = array->n_slots / array->n_segments;
+	/* 64 blocks' striping ( aligning max(BUF_READ_AHEAD_AREA) ) */
+	prim_segment = ( offset >> (UNIV_PAGE_SIZE_SHIFT + 6) ) % (array->n_segments);
+
 loop:
 	os_mutex_enter(array->mutex);
 
@@ -3198,11 +3205,22 @@
 		goto loop;
 	}
 
-	for (i = 0;; i++) {
+	for (i = prim_segment * n; i < array->n_slots; i++) {
 		slot = os_aio_array_get_nth_slot(array, i);
 
 		if (slot->reserved == FALSE) {
 			break;
+		}
+	}
+
+	if (slot->reserved == TRUE){
+		/* Not found after the intended segment. So we should search before. */
+		for (i = 0;; i++) {
+			slot = os_aio_array_get_nth_slot(array, i);
+
+			if (slot->reserved == FALSE) {
+				break;
+			}
 		}
 	}
 
diff -r 4dca80df8ee3 innobase/srv/srv0start.c
--- a/innobase/srv/srv0start.c	Mon Sep 08 16:40:14 2008 -0700
+++ b/innobase/srv/srv0start.c	Mon Sep 08 16:40:20 2008 -0700
@@ -1213,12 +1213,12 @@
 
 	if (!os_aio_use_native_aio) {
  		/* In simulated aio we currently have use only for 4 threads */
-		srv_n_file_io_threads = 4;
+		/*srv_n_file_io_threads = 4;*/
 
 		os_aio_init(8 * SRV_N_PENDING_IOS_PER_THREAD
 						* srv_n_file_io_threads,
 					srv_n_file_io_threads,
-					SRV_MAX_N_PENDING_SYNC_IOS);
+					SRV_MAX_N_PENDING_SYNC_IOS * srv_n_file_io_threads / 4);
 	} else {
 		os_aio_init(SRV_N_PENDING_IOS_PER_THREAD
 						* srv_n_file_io_threads,
diff -r 4dca80df8ee3 patch_info/control_io-threads.info
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/patch_info/control_io-threads.info	Mon Sep 08 16:40:20 2008 -0700
@@ -0,0 +1,6 @@
+File=control_io-threads.patch
+Name=InnoDB patch to control count of IO threads
+Version=1.0
+Author=Yasufumi Kinoshita
+License=BSD
+Comment=