Almost each time when loader opens a file, this leads to calling

disk_open(). Very often this is called several times for one file.
This leads to reading partition table metadata for each call. To
reduce the number of disk I/O we have a simple block cache, but it
is very dumb and more than half of I/O operations related to reading
metadata, misses this cache.

Introduce new cache layer to resolve this problem. It is independent
and doesn't need initialization like bcache, and will work by default
for all loaders which use the new DISK API. A successful disk_open()
call to each new disk or partition produces new entry in the cache.
Even more, when disk was already open, now opening of any nested
partitions does not require reading top level partition table.
So, if without this cache, partition table metadata was read around
20-50 times during boot, now it reads only once. This affects the booting
from GPT and MBR from the UFS.

1 files changed, 9 insertions, 1 deletions

diff --git a/sys/boot/i386/libi386/biosdisk.c b/sys/boot/i386/libi386/biosdisk.c
index 53e7e6a..36bde12 100644
--- a/sys/boot/i386/libi386/biosdisk.c
+++ b/sys/boot/i386/libi386/biosdisk.c
@@ -106,6 +106,7 @@ static int bd_open(struct open_file *f, ...);
 static int bd_close(struct open_file *f);
 static int bd_ioctl(struct open_file *f, u_long cmd, void *data);
 static void bd_print(int verbose);
+static void bd_cleanup(void);
 
 struct devsw biosdisk = {
 	"disk",
@@ -116,7 +117,7 @@ struct devsw biosdisk = {
 	bd_close,
 	bd_ioctl,
 	bd_print,
-	NULL
+	bd_cleanup
 };
 
 /*
@@ -181,6 +182,13 @@ bd_init(void)
 	return(0);
 }
 
+static void
+bd_cleanup(void)
+{
+
+	disk_cleanup(&biosdisk);
+}
+
 /*
  * Try to detect a device supported by the legacy int13 BIOS
  */