svn commit: r201134 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Mon Dec 28 15:35:39 2009
New Revision: 201134
URL: http://svn.freebsd.org/changeset/base/201134

Log:
  Add a knob to allow reclaim of the directory vnodes that are source of
  the namecache records. The reclamation is not enabled by default because
  for typical workload it would make namecache unusable, but large nested
  directory tree easily puts any process that accesses filesystem into 1
  second wait for vlru.
  
  Reported by:	yar (long time ago)
  MFC after:	3 days

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Mon Dec 28 15:06:44 2009	(r201133)
+++ head/sys/kern/vfs_subr.c	Mon Dec 28 15:35:39 2009	(r201134)
@@ -152,6 +152,10 @@ SYSCTL_LONG(_vfs, OID_AUTO, wantfreevnod
 static u_long freevnodes;
 SYSCTL_LONG(_vfs, OID_AUTO, freevnodes, CTLFLAG_RD, &freevnodes, 0, "");
 
+static int vlru_allow_cache_src;
+SYSCTL_INT(_vfs, OID_AUTO, vlru_allow_cache_src, CTLFLAG_RW,
+    &vlru_allow_cache_src, 0, "Allow vlru to reclaim source vnode");
+
 /*
  * Various variables used for debugging the new implementation of
  * reassignbuf().
@@ -643,7 +647,9 @@ vlrureclaim(struct mount *mp)
 		 * If it's been deconstructed already, it's still
 		 * referenced, or it exceeds the trigger, skip it.
 		 */
-		if (vp->v_usecount || !LIST_EMPTY(&(vp)->v_cache_src) ||
+		if (vp->v_usecount ||
+		    (!vlru_allow_cache_src &&
+			!LIST_EMPTY(&(vp)->v_cache_src)) ||
 		    (vp->v_iflag & VI_DOOMED) != 0 || (vp->v_object != NULL &&
 		    vp->v_object->resident_page_count > trigger)) {
 			VI_UNLOCK(vp);
@@ -668,7 +674,9 @@ vlrureclaim(struct mount *mp)
 		 * interlock, the other thread will be unable to drop the
 		 * vnode lock before our VOP_LOCK() call fails.
 		 */
-		if (vp->v_usecount || !LIST_EMPTY(&(vp)->v_cache_src) ||
+		if (vp->v_usecount ||
+		    (!vlru_allow_cache_src &&
+			!LIST_EMPTY(&(vp)->v_cache_src)) ||
 		    (vp->v_object != NULL &&
 		    vp->v_object->resident_page_count > trigger)) {
 			VOP_UNLOCK(vp, LK_INTERLOCK);