Fix a problem with the vfs vnode caching that it doesn't grow quickly

enough and can cause some strange performance problems.  Specifically, at
or near startup time is when the problem is worst.  To reproduce
the problem, run "lat_syscall stat" from the alpha lmbench code right
after bootup.  A positive side effect of this mod is that the name
cache can be set to grow again by sysctl.  A noticable positive
performance impact is realized due to a larger namecache being available
as needed (or tuned.)

2 files changed, 42 insertions, 32 deletions

diff --git a/sys/kern/vfs_export.c b/sys/kern/vfs_export.c
index 98c85b3..3a8c88c 100644
--- a/sys/kern/vfs_export.c
+++ b/sys/kern/vfs_export.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_subr.c	8.31 (Berkeley) 5/26/95
- * $Id: vfs_subr.c,v 1.88 1997/06/22 03:00:21 dyson Exp $
+ * $Id: vfs_subr.c,v 1.89 1997/07/17 07:17:31 dfr Exp $
  */
 
 /*
@@ -354,24 +354,29 @@ getnewvnode(tag, mp, vops, vpp)
 
 	simple_lock(&vnode_free_list_slock);
 
-	TAILQ_FOREACH(vp, &vnode_free_list, v_freelist) {
-		if (!simple_lock_try(&vp->v_interlock)) 
-			continue;
-		if (vp->v_usecount)
-			panic("free vnode isn't");
+	if (freevnodes >= desiredvnodes) {
+		TAILQ_FOREACH(vp, &vnode_free_list, v_freelist) {
+			if (!simple_lock_try(&vp->v_interlock)) 
+				continue;
+			if (vp->v_usecount)
+				panic("free vnode isn't");
 
-		if (vp->v_object && vp->v_object->resident_page_count) {
-			/* Don't recycle if it's caching some pages */
-			simple_unlock(&vp->v_interlock);
-			continue;
-		} else if (LIST_FIRST(&vp->v_cache_src)) {
-			/* Don't recycle if active in the namecache */
-			simple_unlock(&vp->v_interlock);
-			continue;
-		} else {
-			break;
+			if (vp->v_object && vp->v_object->resident_page_count) {
+				/* Don't recycle if it's caching some pages */
+				simple_unlock(&vp->v_interlock);
+				continue;
+			} else if (LIST_FIRST(&vp->v_cache_src)) {
+				/* Don't recycle if active in the namecache */
+				simple_unlock(&vp->v_interlock);
+				continue;
+			} else {
+				break;
+			}
 		}
+	} else {
+		vp = NULL;
 	}
+
 	if (vp) {
 		TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
 		freevnodes--;
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 98c85b3..3a8c88c 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_subr.c	8.31 (Berkeley) 5/26/95
- * $Id: vfs_subr.c,v 1.88 1997/06/22 03:00:21 dyson Exp $
+ * $Id: vfs_subr.c,v 1.89 1997/07/17 07:17:31 dfr Exp $
  */
 
 /*
@@ -354,24 +354,29 @@ getnewvnode(tag, mp, vops, vpp)
 
 	simple_lock(&vnode_free_list_slock);
 
-	TAILQ_FOREACH(vp, &vnode_free_list, v_freelist) {
-		if (!simple_lock_try(&vp->v_interlock)) 
-			continue;
-		if (vp->v_usecount)
-			panic("free vnode isn't");
+	if (freevnodes >= desiredvnodes) {
+		TAILQ_FOREACH(vp, &vnode_free_list, v_freelist) {
+			if (!simple_lock_try(&vp->v_interlock)) 
+				continue;
+			if (vp->v_usecount)
+				panic("free vnode isn't");
 
-		if (vp->v_object && vp->v_object->resident_page_count) {
-			/* Don't recycle if it's caching some pages */
-			simple_unlock(&vp->v_interlock);
-			continue;
-		} else if (LIST_FIRST(&vp->v_cache_src)) {
-			/* Don't recycle if active in the namecache */
-			simple_unlock(&vp->v_interlock);
-			continue;
-		} else {
-			break;
+			if (vp->v_object && vp->v_object->resident_page_count) {
+				/* Don't recycle if it's caching some pages */
+				simple_unlock(&vp->v_interlock);
+				continue;
+			} else if (LIST_FIRST(&vp->v_cache_src)) {
+				/* Don't recycle if active in the namecache */
+				simple_unlock(&vp->v_interlock);
+				continue;
+			} else {
+				break;
+			}
 		}
+	} else {
+		vp = NULL;
 	}
+
 	if (vp) {
 		TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
 		freevnodes--;