Collect read and write counts for filesystems. This new code

drops the counting in bwrite and puts it all in spec_strategy.
I did some tests and verified that the counts collected for writes
in spec_strategy is identical to the counts that we previously
collected in bwrite. We now also get read counts (async reads
come from requests for read-ahead blocks). Note that you need
to compile a new version of mount to get the read counts printed
out. The old mount binary is completely compatible, the only
reason to install a new mount is to get the read counts printed.

Submitted by:	Craig A Soules <soules+@andrew.cmu.edu>
Reviewed by:	Kirk McKusick <mckusick@mckusick.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/sys/fs/specfs/spec_vnops.c b/sys/fs/specfs/spec_vnops.c
index a66597d..9a8ad45 100644
--- a/sys/fs/specfs/spec_vnops.c
+++ b/sys/fs/specfs/spec_vnops.c
@@ -406,11 +406,32 @@ spec_strategy(ap)
 	} */ *ap;
 {
 	struct buf *bp;
+	struct vnode *vp;
+	struct mount *mp;
 
 	bp = ap->a_bp;
 	if (((bp->b_flags & B_READ) == 0) &&
 		(LIST_FIRST(&bp->b_dep)) != NULL && bioops.io_start)
 		(*bioops.io_start)(bp);
+
+	/*
+	 * Collect statistics on synchronous and asynchronous read
+	 * and write counts for disks that have associated filesystems.
+	 */
+	vp = ap->a_vp;
+	if (vn_isdisk(vp) && (mp = vp->v_specmountpoint) != NULL) {
+		if ((bp->b_flags & B_READ) == 0) {
+			if (bp->b_lock.lk_lockholder == LK_KERNPROC)
+				mp->mnt_stat.f_asyncwrites++;
+			else
+				mp->mnt_stat.f_syncwrites++;
+		} else {
+			if (bp->b_lock.lk_lockholder == LK_KERNPROC)
+				mp->mnt_stat.f_asyncreads++;
+			else
+				mp->mnt_stat.f_syncreads++;
+		}
+	}
 	KASSERT(devsw(bp->b_dev) != NULL, 
 	   ("No devsw on dev %s responsible for buffer %p\n", 
 	   devtoname(bp->b_dev), bp));