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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 3 Jun 2013 17:36:44 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r251322 - head/sys/kern
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Author: kib
Date: Mon Jun  3 17:36:43 2013
New Revision: 251322
URL: http://svnweb.freebsd.org/changeset/base/251322

Log:
  Be more generous when donating the current thread time to the owner of
  the vnode lock while iterating over the free vnode list.  Instead of
  yielding, pause for 1 tick.  The change is reported to help in some
  virtualized environments.
  
  Submitted by:	Roger Pau Monn? <roger.pau@citrix.com>
  Discussed with:	jilles
  Tested by:	pho
  MFC after:	2 weeks

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Mon Jun  3 17:36:26 2013	(r251321)
+++ head/sys/kern/vfs_subr.c	Mon Jun  3 17:36:43 2013	(r251322)
@@ -4693,7 +4693,7 @@ restart:
 			if (mp_ncpus == 1 || should_yield()) {
 				TAILQ_INSERT_BEFORE(vp, *mvp, v_actfreelist);
 				mtx_unlock(&vnode_free_list_mtx);
-				kern_yield(PRI_USER);
+				pause("vnacti", 1);
 				mtx_lock(&vnode_free_list_mtx);
 				goto restart;
 			}