Revert commit 8733bc277a

Author: Mateusz Guzik <[email protected]>
Date:   Thu Sep 14 16:13:01 2023 +0000

    vfs: don't provoke recycling non-free vnodes without a good reason

    If the total number of free vnodes is at or above target, there is no
    point creating more of them.

This commit was done as a performance optimization but ends up
causing slowdowns when doing operations on many files.

Requested by:   re (cperciva)
MFC after:      1 minute

sys/kern/vfs_subr.c

@@ -1992,25 +1992,11 @@ vn_alloc_hard(struct mount *mp, u_long rnumvnodes, bool bumped)
 
 	mtx_lock(&vnode_list_mtx);
 
-	if (vn_alloc_cyclecount != 0) {
-		rnumvnodes = atomic_load_long(&numvnodes);
-		if (rnumvnodes + 1 < desiredvnodes) {
-			vn_alloc_cyclecount = 0;
-			mtx_unlock(&vnode_list_mtx);
-			goto alloc;
-		}
-
-		rfreevnodes = vnlru_read_freevnodes();
-		if (rfreevnodes < wantfreevnodes) {
-			if (vn_alloc_cyclecount++ >= rfreevnodes) {
-				vn_alloc_cyclecount = 0;
-				vstir = true;
-			}
-		} else {
-			vn_alloc_cyclecount = 0;
-		}
+	rfreevnodes = vnlru_read_freevnodes();
+	if (vn_alloc_cyclecount++ >= rfreevnodes) {
+		vn_alloc_cyclecount = 0;
+		vstir = true;
 	}
-
 	/*
 	 * Grow the vnode cache if it will not be above its target max after
 	 * growing.  Otherwise, if there is at least one free vnode, try to