After extensive testing it has been determined that adding complexity

to avoid removing higher level directory vnodes from the namecache has
no perceivable effect and will be removed.  This is especially true
when vmiodirenable is turned on, which it is by default now.  ( vmiodirenable
makes a huge difference in directory caching ).  The vfs.vmiodirenable and
vfs.nameileafonly sysctls have been left in to allow further testing, but
I expect to rip out vfs.nameileafonly soon too.

I have also determined through testing that the real problem with numvnodes
getting too large is due to the VM Page cache preventing the vnode from
being reclaimed.  The directory stuff made only a tiny dent relative
to Poul's original code, enough so that some tests succeeded.  But tests
with several million small files show that the bigger problem is the VM Page
cache.  This will have to be addressed by a future commit.

MFC after:	3 days

1 files changed, 68 insertions, 29 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 8c67662..8fdd423 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -110,6 +110,8 @@ SYSCTL_LONG(_debug, OID_AUTO, wantfreevnodes, CTLFLAG_RW, &wantfreevnodes, 0, ""
 /* Number of vnodes in the free list. */
 static u_long freevnodes = 0;
 SYSCTL_LONG(_debug, OID_AUTO, freevnodes, CTLFLAG_RD, &freevnodes, 0, "");
+
+#if 0
 /* Number of vnode allocation. */
 static u_long vnodeallocs = 0;
 SYSCTL_LONG(_debug, OID_AUTO, vnodeallocs, CTLFLAG_RD, &vnodeallocs, 0, "");
@@ -125,6 +127,7 @@ SYSCTL_LONG(_debug, OID_AUTO, vnoderecycleminfreevn, CTLFLAG_RW, &vnoderecyclemi
 /* Number of vnodes attempted to recycle at a time. */
 static u_long vnoderecyclenumber = 3000;
 SYSCTL_LONG(_debug, OID_AUTO, vnoderecyclenumber, CTLFLAG_RW, &vnoderecyclenumber, 0, "");
+#endif
 
 /*
  * Various variables used for debugging the new implementation of
@@ -142,6 +145,8 @@ SYSCTL_INT(_vfs, OID_AUTO, reassignbufsortbad, CTLFLAG_RW, &reassignbufsortbad,
 /* Set to 0 for old insertion-sort based reassignbuf, 1 for modern method. */
 static int reassignbufmethod = 1;
 SYSCTL_INT(_vfs, OID_AUTO, reassignbufmethod, CTLFLAG_RW, &reassignbufmethod, 0, "");
+static int nameileafonly = 0;
+SYSCTL_INT(_vfs, OID_AUTO, nameileafonly, CTLFLAG_RW, &nameileafonly, 0, "");
 
 #ifdef ENABLE_VFS_IOOPT
 /* See NOTES for a description of this setting. */
@@ -238,6 +243,9 @@ SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW, &stat_rush_requests, 0,
 int desiredvnodes;
 SYSCTL_INT(_kern, KERN_MAXVNODES, maxvnodes, CTLFLAG_RW, 
     &desiredvnodes, 0, "Maximum number of vnodes");
+static int minvnodes; 
+SYSCTL_INT(_kern, KERN_MAXVNODES, minvnodes, CTLFLAG_RW,
+    &minvnodes, 0, "Minimum number of vnodes");
 
 /*
  * Initialize the vnode management data structures.
@@ -247,6 +255,7 @@ vntblinit(void *dummy __unused)
 {
 
 	desiredvnodes = maxproc + cnt.v_page_count / 4;
+	minvnodes = desiredvnodes / 4;
 	mtx_init(&mountlist_mtx, "mountlist", MTX_DEF);
 	mtx_init(&mntvnode_mtx, "mntvnode", MTX_DEF);
 	mtx_init(&mntid_mtx, "mntid", MTX_DEF);
@@ -539,40 +548,68 @@ getnewvnode(tag, mp, vops, vpp)
 	s = splbio();
 	mtx_lock(&vnode_free_list_mtx);
 
-	if (wantfreevnodes && freevnodes < wantfreevnodes) {
-		vp = NULL;
-	} else if (!wantfreevnodes && freevnodes <= desiredvnodes) {
-		/* 
-		 * XXX: this is only here to be backwards compatible
-		 */
+	if (freevnodes < wantfreevnodes) {
 		vp = NULL;
-	} else for (count = 0; count < freevnodes; count++) {
-		vp = TAILQ_FIRST(&vnode_free_list);
-		if (vp == NULL || vp->v_usecount)
-			panic("getnewvnode: free vnode isn't");
-		TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
+	} else if (numvnodes >= minvnodes) {
+		for (count = 0; count < freevnodes; count++) {
+			vp = TAILQ_FIRST(&vnode_free_list);
+			if (vp == NULL || vp->v_usecount)
+				panic("getnewvnode: free vnode isn't");
+			TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
 
-		/*
-		 * Don't recycle if active in the namecache or
-		 * if it still has cached pages or we cannot get
-		 * its interlock.
-		 */
-		if (LIST_FIRST(&vp->v_cache_src) != NULL ||
-		    (VOP_GETVOBJECT(vp, &object) == 0 &&
-		     (object->resident_page_count || object->ref_count)) ||
-		    !mtx_trylock(&vp->v_interlock)) {
+			/*
+			 * Don't recycle if we still have cached pages or if
+			 * we cannot get the interlock.
+			 */
+			if ((VOP_GETVOBJECT(vp, &object) == 0 &&
+			     (object->resident_page_count ||
+			      object->ref_count)) ||
+			     !mtx_trylock(&vp->v_interlock)) {
+				TAILQ_INSERT_TAIL(&vnode_free_list, vp,
+						    v_freelist);
+				vp = NULL;
+				continue;
+			}
+			if (LIST_FIRST(&vp->v_cache_src)) {
+				/*
+				 * note: nameileafonly sysctl is temporary,
+				 * for debugging only, and will eventually be
+				 * removed.
+				 */
+				if (nameileafonly > 0) {
+					/*
+					 * Do not reuse namei-cached directory
+					 * vnodes that have cached
+					 * subdirectories.
+					 */
+					if (cache_leaf_test(vp) < 0) {
+						mtx_unlock(&vp->v_interlock);
+						vp = NULL;
+						continue;
+					}
+				} else if (nameileafonly < 0 ||
+					    vmiodirenable == 0) {
+					/*
+					 * Do not reuse namei-cached directory
+					 * vnodes if nameileafonly is -1 or
+					 * if VMIO backing for directories is
+					 * turned off (otherwise we reuse them
+					 * too quickly).
+					 */
+					mtx_unlock(&vp->v_interlock);
+					vp = NULL;
+					continue;
+				}
+			}
+			/*
+			 * Skip over it if its filesystem is being suspended.
+			 */
+			if (vn_start_write(vp, &vnmp, V_NOWAIT) == 0)
+				break;
+			mtx_unlock(&vp->v_interlock);
 			TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
 			vp = NULL;
-			continue;
 		}
-		/*
-		 * Skip over it if its filesystem is being suspended.
-		 */
-		if (vn_start_write(vp, &vnmp, V_NOWAIT) == 0)
-			break;
-		mtx_unlock(&vp->v_interlock);
-		TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
-		vp = NULL;
 	}
 	if (vp) {
 		vp->v_flag |= VDOOMED;
@@ -636,6 +673,7 @@ getnewvnode(tag, mp, vops, vpp)
 
 	vfs_object_create(vp, td, td->td_proc->p_ucred);
 
+#if 0
 	vnodeallocs++;
 	if (vnodeallocs % vnoderecycleperiod == 0 &&
 	    freevnodes < vnoderecycleminfreevn &&
@@ -643,6 +681,7 @@ getnewvnode(tag, mp, vops, vpp)
 		/* Recycle vnodes. */
 		cache_purgeleafdirs(vnoderecyclenumber);
 	}
+#endif
 
 	return (0);
 }