This is a stupid simple diff to see just how much time you spend
waiting for your disk. If you're into measuring that kind of thing.
Index: vfs_bio.c
===================================================================
RCS file: /cvs/src/sys/kern/vfs_bio.c,v
retrieving revision 1.146
diff -u -p -r1.146 vfs_bio.c
--- vfs_bio.c 17 Feb 2013 17:39:29 -0000 1.146
+++ vfs_bio.c 5 Apr 2013 01:34:03 -0000
@@ -1153,6 +1153,8 @@ buf_daemon(struct proc *p)
}
}
+uint64_t biowaittime;
+
/*
* Wait for operations on the buffer to complete.
* When they do, extract and return the I/O's error value.
@@ -1161,12 +1163,18 @@ int
biowait(struct buf *bp)
{
int s;
+ struct timespec before, after, diff;
KASSERT(!(bp->b_flags & B_ASYNC));
s = splbio();
+ nanotime(&before);
while (!ISSET(bp->b_flags, B_DONE))
tsleep(bp, PRIBIO + 1, "biowait", 0);
+ nanotime(&after);
+ timespecsub(&after, &before, &diff);
+ biowaittime += diff.tv_nsec;
+ biowaittime += diff.tv_sec * 1000000000L;
splx(s);
/* check for interruption of I/O (e.g. via NFS), then errors. */
