diff --git a/sys/i386/include/param.h b/sys/i386/include/param.h
index b494f35..2d5f4a5 100644
--- a/sys/i386/include/param.h
+++ b/sys/i386/include/param.h
@@ -140,9 +140,12 @@
  * Ceiling on size of buffer cache (really only effects write queueing,
  * the VM page cache is not effected), can be changed via
  * the kern.maxbcache /boot/loader.conf variable.
+ *
+ * The value is equal to the size of the auto-tuned buffer map for
+ * the machine with 4GB of RAM, see vfs_bio.c:kern_vfs_bio_buffer_alloc().
  */
 #ifndef VM_BCACHE_SIZE_MAX
-#define VM_BCACHE_SIZE_MAX	(200 * 1024 * 1024)
+#define VM_BCACHE_SIZE_MAX	(7224 * 16 * 1024)
 #endif
 
 /*
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 30f935c..14f5b3d 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -579,7 +579,7 @@ kern_vfs_bio_buffer_alloc(caddr_t v, long physmem_est)
 	 * to the amount of the buffer mapped for typical UFS load.
 	 *
 	 * Clip the buffer map to reserve space for the transient
-	 * BIOs, if its extent is bigger than 90% of the maximum
+	 * BIOs, if its extent is bigger than 80% of the maximum
 	 * buffer map extent on the platform.
 	 *
 	 * The fall-back to the maxbuf in case of maxbcache unset,
@@ -589,7 +589,7 @@ kern_vfs_bio_buffer_alloc(caddr_t v, long physmem_est)
 	if (bio_transient_maxcnt == 0 && unmapped_buf_allowed) {
 		maxbuf_sz = maxbcache != 0 ? maxbcache : maxbuf * BKVASIZE;
 		buf_sz = (long)nbuf * BKVASIZE;
-		if (buf_sz < maxbuf_sz / 10 * 9) {
+		if (buf_sz < maxbuf_sz / 5 * 4) {
 			/*
 			 * There is more KVA than memory.  Do not
 			 * adjust buffer map size, and assign the rest
@@ -599,10 +599,10 @@ kern_vfs_bio_buffer_alloc(caddr_t v, long physmem_est)
 		} else {
 			/*
 			 * Buffer map spans all KVA we could afford on
-			 * this platform.  Give 10% of the buffer map
+			 * this platform.  Give 20% of the buffer map
 			 * to the transient bio map.
 			 */
- 			biotmap_sz = buf_sz / 10;
+			biotmap_sz = buf_sz / 5;
 			buf_sz -= biotmap_sz;
 		}
 		if (biotmap_sz / INT_MAX > MAXPHYS)