Implement NFS ACCESS RPC result caching.

This yields startling performance increases for NFS clients for many
access profiles, due to the fact that ACCESS results are persistently
cached in the namecache in many cases.

Note that the code is somewhat conservative in that it requires an
exact credential match for a cache hit.  This bloats the nfsnode
structure by sizeof(struct ucred) (96 bytes).  Any less conservative
approach opens the possibility for a false veto in eg. setuid
applications.  Alternative suggestions would be welcomed.

The cache is normally disabled, to activate set the sysctl variable
vfs.nfs.access_cache_timeout to a nonzero value.  This is the time in
seconds that a cached entry will be considered valid; useful values appear
to be 2-10 seconds.  Performance of the cache can be monitored with the
vfs.nfs.access_cache_hits and vfs.nfs.access_cache_hits variables.

1 files changed, 4 insertions, 1 deletions

diff --git a/sys/nfs/nfsnode.h b/sys/nfs/nfsnode.h
index 51f5d78..b242216 100644
--- a/sys/nfs/nfsnode.h
+++ b/sys/nfs/nfsnode.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)nfsnode.h	8.9 (Berkeley) 5/14/95
- * $Id: nfsnode.h,v 1.25 1998/03/06 09:46:52 msmith Exp $
+ * $Id: nfsnode.h,v 1.26 1998/05/31 18:32:23 peter Exp $
  */
 
 
@@ -93,6 +93,9 @@ struct nfsnode {
 	u_quad_t		n_lrev;		/* Modify rev for lease */
 	struct vattr		n_vattr;	/* Vnode attribute cache */
 	time_t			n_attrstamp;	/* Attr. cache timestamp */
+	u_int32_t		n_mode;		/* ACCESS mode cache */
+	struct ucred		n_modecred;	/* credentials having mode */
+	time_t			n_modestamp;	/* mode cache timestamp */
 	time_t			n_mtime;	/* Prev modify time. */
 	time_t			n_ctime;	/* Prev create time. */
 	time_t			n_expiry;	/* Lease expiry time */