svn commit: r255835 - head/sys/kern

[Alexander Motin]

Author: mav
Date: Tue Sep 24 07:03:16 2013
New Revision: 255835
URL: http://svnweb.freebsd.org/changeset/base/255835

Log:
  Make load average sampling asynchronous to hardclock ticks. This improves
  measurement of load caused by time-related events still using hardclock.
  For example, without this change dummynet, scheduling events each hardclock
  tick, was always miscounted as load of 1.
  
  There is still aliasing with events delayed by the new precision mechanism,
  but it probably can't be avoided without moving this sampling from using
  callout to some lower-level code or handling it in some other special way.
  
  Reviewed by:	davide
  Approved by:	re (marius)

Modified:
  head/sys/kern/kern_synch.c

Modified: head/sys/kern/kern_synch.c
==============================================================================
--- head/sys/kern/kern_synch.c	Tue Sep 24 06:48:28 2013	(r255834)
+++ head/sys/kern/kern_synch.c	Tue Sep 24 07:03:16 2013	(r255835)
@@ -570,8 +570,8 @@ loadav(void *arg)
 	 * run at regular intervals.
 	 */
 	callout_reset_sbt(&loadav_callout,
-	    tick_sbt * (hz * 4 + (int)(random() % (hz * 2 + 1))), 0,
-	    loadav, NULL, C_DIRECT_EXEC | C_HARDCLOCK);
+	    SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
+	    loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
 }
 
 /* ARGSUSED */