Implement a simple LRU block cache. By default this is initialised to 16k,

and will bypass transfers for more than 8k.  Blocks are invalidated after
2 seconds, so removable media should not confuse the cache.

The 8k threshold is a compromise; all UFS transfers performed by
libstand are 8k or less, so large file reads thrash the cache.
However many filesystem metadata operations are also performed using
8k blocks, so using a lower threshold gives poor performance.

Those of you with an eye for cache algorithms are welcome to tell me
how badly this one sucks; you can start with the 'bcachestats' command
which will print the contents of the cache and access statistics.

1 files changed, 6 insertions, 1 deletions

diff --git a/sys/boot/alpha/common/main.c b/sys/boot/alpha/common/main.c
index 2776b08..4140024 100644
--- a/sys/boot/alpha/common/main.c
+++ b/sys/boot/alpha/common/main.c
@@ -24,7 +24,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: main.c,v 1.7 1998/10/24 00:31:21 msmith Exp $
+ *	$Id: main.c,v 1.8 1998/10/31 17:12:32 dfr Exp $
  */
 
 
@@ -142,6 +142,11 @@ main(void)
     OSFpal();
 
     /*
+     * Initialise the block cache
+     */
+    bcache_init(32, 512);	/* 16k XXX tune this */
+
+    /*
      * March through the device switch probing for things.
      */
     for (i = 0; devsw[i] != NULL; i++)