svn commit: r254544 - head/sys/vm

[Jeff Roberson]

Author: jeff
Date: Mon Aug 19 23:54:24 2013
New Revision: 254544
URL: http://svnweb.freebsd.org/changeset/base/254544

Log:
   - Increase the active lru refresh interval to 10 minutes.  This has been
     shown to negatively impact some workloads and the goal is only to
     eliminate worst case behaviors for very long periods of paging
     inactivity.  Eventually we should determine a more complex scaling
     factor for this feature.
   - Rate limit low memory callback handlers to limit thrashing.  Set the
     default to 10 seconds.
  
  Sponsored by:	EMC / Isilon Storage Division

Modified:
  head/sys/vm/vm_pageout.c

Modified: head/sys/vm/vm_pageout.c
==============================================================================
--- head/sys/vm/vm_pageout.c	Mon Aug 19 23:02:39 2013	(r254543)
+++ head/sys/vm/vm_pageout.c	Mon Aug 19 23:54:24 2013	(r254544)
@@ -159,6 +159,8 @@ static int vm_max_launder = 32;
 static int vm_pageout_update_period;
 static int defer_swap_pageouts;
 static int disable_swap_pageouts;
+static int lowmem_period = 10;
+static int lowmem_ticks;
 
 #if defined(NO_SWAPPING)
 static int vm_swap_enabled = 0;
@@ -179,6 +181,9 @@ SYSCTL_INT(_vm, OID_AUTO, pageout_update
 	CTLFLAG_RW, &vm_pageout_update_period, 0,
 	"Maximum active LRU update period");
   
+SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
+	"Low memory callback period");
+
 #if defined(NO_SWAPPING)
 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 	CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
@@ -901,9 +906,10 @@ vm_pageout_scan(struct vm_domain *vmd, i
 
 	/*
 	 * If we need to reclaim memory ask kernel caches to return
-	 * some.
+	 * some.  We rate limit to avoid thrashing.
 	 */
-	if (pass > 0) {
+	if (vmd == &vm_dom[0] && pass > 0 &&
+	    lowmem_ticks + (lowmem_period * hz) < ticks) {
 		/*
 		 * Decrease registered cache sizes.
 		 */
@@ -913,6 +919,7 @@ vm_pageout_scan(struct vm_domain *vmd, i
 		 * drained above.
 		 */
 		uma_reclaim();
+		lowmem_ticks = ticks;
 	}
 
 	/*
@@ -1680,10 +1687,11 @@ vm_pageout(void)
 
 	/*
 	 * Set interval in seconds for active scan.  We want to visit each
-	 * page at least once a minute.
+	 * page at least once every ten minutes.  This is to prevent worst
+	 * case paging behaviors with stale active LRU.
 	 */
 	if (vm_pageout_update_period == 0)
-		vm_pageout_update_period = 60;
+		vm_pageout_update_period = 600;
 
 	/* XXX does not really belong here */
 	if (vm_page_max_wired == 0)