These changes fix a couple of lingering VM problems:

1.	The pageout daemon used to block under certain
	circumstances, and we needed to add new functionality
	that would cause the pageout daemon to block more often.
	Now, the pageout daemon mostly just gets rid of pages
	and kills processes when the system is out of swap.
	The swapping, rss limiting and object cache trimming
	have been folded into a new daemon called "vmdaemon".
	This new daemon does things that need to be done for
	the VM system, but can block.  For example, if the
	vmdaemon blocks for memory, the pageout daemon
	can take care of it.  If the pageout daemon had
	blocked for memory, it was difficult to handle
	the situation correctly (and in some cases, was
	impossible).

2.	The collapse problem has now been entirely fixed.
	It now appears to be impossible to accumulate unnecessary
	vm objects.  The object collapsing now occurs when ref counts
	drop to one (where it is more likely to be more simple anyway
	because less pages would be out on disk.)  The original
	fixes were incomplete in that pathological circumstances
	could still be contrived to cause uncontrolled growth
	of swap.  Also, the old code still, under steady state
	conditions, used more swap space than necessary.  When
	using the new code, users will generally notice a
	significant decrease in swap space usage, and theoretically,
	the system should be leaving fewer unused pages around
	competing for memory.

Submitted by:	John Dyson

3 files changed, 5 insertions, 110 deletions

diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index f42f00a..8a49935 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)init_main.c	8.9 (Berkeley) 1/21/94
- * $Id: init_main.c,v 1.15 1994/10/26 03:34:20 phk Exp $
+ * $Id: init_main.c,v 1.16 1994/11/06 05:01:58 davidg Exp $
  */
 
 #include <sys/param.h>
@@ -319,7 +319,6 @@ main(framep)
 		/* NOTREACHED */
 	}
 
-#ifdef REL2_1
 	/*
 	 * Start high level vm daemon (process 3).
 	 */
@@ -333,7 +332,6 @@ main(framep)
 		vm_daemon();
 		/*NOTREACHED*/
 	}
-#endif
 
 	/*
 	 * Start update daemon (process 4).
diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 66159af..75c4079 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -61,7 +61,7 @@
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
- * $Id: vm_object.c,v 1.9 1994/10/15 10:28:46 davidg Exp $
+ * $Id: vm_object.c,v 1.10 1994/11/06 05:07:50 davidg Exp $
  */
 
 /*
@@ -127,9 +127,7 @@ _vm_object_allocate(size, object)
 {
 	bzero(object, sizeof *object);
 	TAILQ_INIT(&object->memq);
-#ifdef REL2_1a
 	TAILQ_INIT(&object->reverse_shadow_head);
-#endif
 	vm_object_lock_init(object);
 	object->ref_count = 1;
 	object->resident_page_count = 0;
@@ -253,10 +251,8 @@ vm_object_deallocate(object)
 		 */
 		vm_object_lock(object);
 		if (--(object->ref_count) != 0) {
-#ifdef REL2_1a
 			if( object->ref_count == 1)
 				vm_object_rcollapse(object->reverse_shadow_head.tqh_first, object);
-#endif
 
 			vm_object_unlock(object);
 			/*
@@ -299,10 +295,8 @@ vm_object_deallocate(object)
 		vm_object_cache_unlock();
 	
 		temp = object->shadow;
-#ifdef REL2_1a
 		if( temp)
 			TAILQ_REMOVE(&temp->reverse_shadow_head, object, reverse_shadow_list);
-#endif
 		vm_object_terminate(object);
 			/* unlocks and deallocates object */
 		object = temp;
@@ -917,14 +911,10 @@ void vm_object_copy(src_object, src_offset, size,
 		 */
 
 		src_object->ref_count--;	/* remove ref. from old_copy */
-#ifdef REL2_1a
 		if( old_copy->shadow)
 			TAILQ_REMOVE(&old_copy->shadow->reverse_shadow_head, old_copy, reverse_shadow_list);
-#endif
 		old_copy->shadow = new_copy;
-#ifdef REL2_1a
 		TAILQ_INSERT_TAIL(&old_copy->shadow->reverse_shadow_head, old_copy, reverse_shadow_list);
-#endif
 		new_copy->ref_count++;		/* locking not needed - we
 						   have the only pointer */
 		vm_object_unlock(old_copy);	/* done with old_copy */
@@ -938,9 +928,7 @@ void vm_object_copy(src_object, src_offset, size,
 	 */
 
 	new_copy->shadow = src_object;
-#ifdef REL2_1a
 	TAILQ_INSERT_TAIL(&new_copy->shadow->reverse_shadow_head, new_copy, reverse_shadow_list);
-#endif
 	new_copy->shadow_offset = new_start;
 	src_object->ref_count++;
 	src_object->copy = new_copy;
@@ -997,9 +985,7 @@ vm_object_shadow(object, offset, length)
 	 *	count.
 	 */
 	result->shadow = source;
-#ifdef REL2_1a
 	TAILQ_INSERT_TAIL(&result->shadow->reverse_shadow_head, result, reverse_shadow_list);
-#endif
 	
 	/*
 	 *	Store the offset into the source object,
@@ -1148,7 +1134,6 @@ vm_object_remove(pager)
 	}
 }
 
-#ifdef REL2_1a
 static void
 vm_object_rcollapse(object, sobject)
 	register vm_object_t object, sobject;
@@ -1212,7 +1197,6 @@ vm_object_rcollapse(object, sobject)
 		}
 	}
 }
-#endif
 
 /*
  * this version of collapse allows the operation to occur earlier and
@@ -1483,17 +1467,13 @@ vm_object_collapse(object)
 			 *	moves from within backing_object to within object.
 			 */
 
-#ifdef REL2_1a
 			TAILQ_REMOVE(&object->shadow->reverse_shadow_head, object, reverse_shadow_list);
 			if( backing_object->shadow)
 				TAILQ_REMOVE(&backing_object->shadow->reverse_shadow_head, backing_object, reverse_shadow_list);
-#endif
 			object->shadow = backing_object->shadow;
-#ifdef REL2_1a
 			if( object->shadow)
 				TAILQ_INSERT_TAIL(&object->shadow->reverse_shadow_head, object, reverse_shadow_list);
-#endif
-				
+
 			object->shadow_offset += backing_object->shadow_offset;
 			if (object->shadow != NULL &&
 			    object->shadow->copy != NULL) {
@@ -1574,14 +1554,10 @@ vm_object_collapse(object)
 			 *	count is at least 2.
 			 */
 
-#ifdef REL2_1a
 			TAILQ_REMOVE(&object->shadow->reverse_shadow_head, object, reverse_shadow_list);
-#endif
 			vm_object_reference(object->shadow = backing_object->shadow);
-#ifdef REL2_1a
 			if( object->shadow)
 				TAILQ_INSERT_TAIL(&object->shadow->reverse_shadow_head, object, reverse_shadow_list);
-#endif
 			object->shadow_offset += backing_object->shadow_offset;
 
 			/*
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 37267d3..e2fd22c 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -65,7 +65,7 @@
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
- * $Id: vm_pageout.c,v 1.25 1994/11/14 02:57:40 davidg Exp $
+ * $Id: vm_pageout.c,v 1.26 1994/11/17 06:24:25 davidg Exp $
  */
 
 /*
@@ -343,20 +343,10 @@ vm_pageout_object_deactivate_pages(map, object, count)
 	if (count == 0)
 		count = 1;
 
-#ifndef REL2_1
-	if (object->shadow) {
-		int scount = count;
-		if( object->shadow->ref_count > 1)
-			scount /= object->shadow->ref_count;
-		if( scount)
-			dcount += vm_pageout_object_deactivate_pages(map, object->shadow, scount);
-	}
-#else
 	if (object->shadow) {
 		if( object->shadow->ref_count == 1)
 			dcount += vm_pageout_object_deactivate_pages(map, object->shadow, count/2);
 	}
-#endif
 
 	if (object->paging_in_progress)
 		return dcount;
@@ -479,7 +469,6 @@ vm_pageout_map_deactivate_pages(map, entry, count, freeer)
 	return;
 }
 
-#ifdef REL2_1
 void
 vm_req_vmdaemon() {
 	extern	int ticks;
@@ -489,7 +478,6 @@ vm_req_vmdaemon() {
 		lastrun = ticks;
 	}
 }
-#endif
 
 /*
  *	vm_pageout_scan does the dirty work for the pageout daemon.
@@ -508,69 +496,6 @@ vm_pageout_scan()
 	int		force_wakeup = 0;
 	int		cache_size, orig_cache_size;
 
-#ifndef REL2_1
-morefree:
-	/*
-	 * now swap processes out if we are in low memory conditions
-	 */
-	if ((cnt.v_free_count <= cnt.v_free_min) && !swap_pager_full && vm_swap_size) {
-		/*
-		 * swap out inactive processes
-		 */
-		swapout_threads();
-	}
-
-	/*
-	 * scan the processes for exceeding their rlimits or if process
-	 * is swapped out -- deactivate pages 
-	 */
-
-	for (p = (struct proc *)allproc; p != NULL; p = p->p_next) {
-		int overage;
-		quad_t limit;
-
-		/*
-		 * if this is a system process or if we have already
-		 * looked at this process, skip it.
-		 */
-		if (p->p_flag & (P_SYSTEM|P_WEXIT)) {
-			continue;
-		}
-
-		/*
-		 * if the process is in a non-running type state,
-		 * don't touch it.
-		 */
-		if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
-			continue;
-		}
-
-		/*
-		 * get a limit
-		 */
-		limit = qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
-			    p->p_rlimit[RLIMIT_RSS].rlim_max);
-			
-		/*
-		 * let processes that are swapped out really be swapped out
-		 * set the limit to nothing (will force a swap-out.)
-		 */
-		if ((p->p_flag & P_INMEM) == 0)
-			limit = 0;
-
-		size = p->p_vmspace->vm_pmap.pm_stats.resident_count * NBPG;
-		if (limit >= 0 && size >= limit) {
-			overage = (size - limit) / NBPG;
-			vm_pageout_map_deactivate_pages(&p->p_vmspace->vm_map,
-				(vm_map_entry_t) 0, &overage, vm_pageout_object_deactivate_pages);
-		}
-	}
-
-	if (((cnt.v_free_count + cnt.v_inactive_count) >=
-		(cnt.v_inactive_target + cnt.v_free_target)) &&
-		(cnt.v_free_count >= cnt.v_free_target))
-		return force_wakeup;
-#else
 	/* calculate the total cached size */
 
 	if( cnt.v_inactive_count < cnt.v_inactive_target) {
@@ -586,8 +511,6 @@ morefree:
 		vm_req_vmdaemon();
 	}
 
-#endif
-
 	pages_freed = 0;
 	desired_free = cnt.v_free_target;
 
@@ -598,7 +521,7 @@ morefree:
 	 *	encounter dirty pages, we start cleaning them.
 	 */
 
-	maxlaunder = (cnt.v_free_target - cnt.v_free_count);
+	maxlaunder = 128;
 	maxscan = cnt.v_inactive_count;
 rescan1:
 	m = vm_page_queue_inactive.tqh_first;
@@ -891,7 +814,6 @@ vm_pageout()
 	}
 }
 
-#ifdef REL2_1
 void
 vm_daemon() {
 	int cache_size;
@@ -994,4 +916,3 @@ restart:
 		vm_object_cache_unlock();
 	}
 }
-#endif