add a uvm_yield function and use it in the reaper path to prevent the

reaper from hogging the cpu. it will do the kernel lock twiddle trick to
allow other CPUs a chance to run, and also checks if the reaper has been
running for an entire timeslice and should be preempted.
ok deraadt

3 files changed, 27 insertions, 9 deletions

diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
index 9a49d2d3043..06919d70979 100644
--- a/sys/uvm/uvm_extern.h
+++ b/sys/uvm/uvm_extern.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_extern.h,v 1.111 2014/03/28 17:57:11 mpi Exp $	*/
+/*	$OpenBSD: uvm_extern.h,v 1.112 2014/04/03 21:40:10 tedu Exp $	*/
 /*	$NetBSD: uvm_extern.h,v 1.57 2001/03/09 01:02:12 chs Exp $	*/
 
 /*
@@ -527,6 +527,7 @@ int			uvm_vslock_device(struct proc *, void *, size_t,
 			    vm_prot_t, void **);
 void			uvm_vsunlock_device(struct proc *, void *, size_t,
 			    void *);
+void			uvm_pause(void);
 
 
 /* uvm_init.c */
diff --git a/sys/uvm/uvm_glue.c b/sys/uvm/uvm_glue.c
index 54aabfec330..62c7d152527 100644
--- a/sys/uvm/uvm_glue.c
+++ b/sys/uvm/uvm_glue.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_glue.c,v 1.60 2013/03/31 17:06:34 deraadt Exp $	*/
+/*	$OpenBSD: uvm_glue.c,v 1.61 2014/04/03 21:40:10 tedu Exp $	*/
 /*	$NetBSD: uvm_glue.c,v 1.44 2001/02/06 19:54:44 eeh Exp $	*/
 
 /* 
@@ -475,4 +475,13 @@ uvm_atopg(vaddr_t kva)
 	pg = PHYS_TO_VM_PAGE(pa);
 	KASSERT(pg != NULL);
 	return (pg);
-} 
+}
+
+void
+uvm_pause(void)
+{
+	KERNEL_UNLOCK();
+	KERNEL_LOCK();
+	if (curcpu()->ci_schedstate.spc_schedflags & SPCF_SHOULDYIELD)
+		preempt(NULL);
+}
diff --git a/sys/uvm/uvm_map.c b/sys/uvm/uvm_map.c
index f35a3864029..41a266cbb53 100644
--- a/sys/uvm/uvm_map.c
+++ b/sys/uvm/uvm_map.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.c,v 1.164 2014/01/23 22:06:30 miod Exp $	*/
+/*	$OpenBSD: uvm_map.c,v 1.165 2014/04/03 21:40:10 tedu Exp $	*/
 /*	$NetBSD: uvm_map.c,v 1.86 2000/11/27 08:40:03 chs Exp $	*/
 
 /*
@@ -1381,8 +1381,12 @@ void
 uvm_unmap_detach(struct uvm_map_deadq *deadq, int flags)
 {
 	struct vm_map_entry *entry;
+	int waitable;
 
+	waitable = flags & UVM_PLA_WAITOK;
 	while ((entry = TAILQ_FIRST(deadq)) != NULL) {
+		if (waitable)
+			uvm_pause();
 		/*
 		 * Drop reference to amap, if we've got one.
 		 */
@@ -1390,7 +1394,7 @@ uvm_unmap_detach(struct uvm_map_deadq *deadq, int flags)
 			amap_unref(entry->aref.ar_amap,
 			    entry->aref.ar_pageoff,
 			    atop(entry->end - entry->start),
-			    flags);
+			    flags & AMAP_REFALL);
 
 		/*
 		 * Drop reference to our backing object, if we've got one.
@@ -2322,13 +2326,15 @@ void
 uvm_map_teardown(struct vm_map *map)
 {
 	struct uvm_map_deadq	 dead_entries;
-	int			 i;
+	int			 i, waitable = 0;
 	struct vm_map_entry	*entry, *tmp;
 #ifdef VMMAP_DEBUG
 	size_t			 numq, numt;
 #endif
 
-	if ((map->flags & VM_MAP_INTRSAFE) == 0) {
+	if ((map->flags & VM_MAP_INTRSAFE) == 0)
+		waitable = 1;
+	if (waitable) {
 		if (rw_enter(&map->lock, RW_NOSLEEP | RW_WRITE) != 0)
 			panic("uvm_map_teardown: rw_enter failed on free map");
 	}
@@ -2366,6 +2372,8 @@ uvm_map_teardown(struct vm_map *map)
 	if ((entry = RB_ROOT(&map->addr)) != NULL)
 		DEAD_ENTRY_PUSH(&dead_entries, entry);
 	while (entry != NULL) {
+		if (waitable)
+			uvm_pause();
 		uvm_unmap_kill_entry(map, entry);
 		if ((tmp = RB_LEFT(entry, daddrs.addr_entry)) != NULL)
 			DEAD_ENTRY_PUSH(&dead_entries, tmp);
@@ -2375,7 +2383,7 @@ uvm_map_teardown(struct vm_map *map)
 		entry = TAILQ_NEXT(entry, dfree.deadq);
 	}
 
-	if ((map->flags & VM_MAP_INTRSAFE) == 0)
+	if (waitable)
 		rw_exit(&map->lock);
 
 #ifdef VMMAP_DEBUG
@@ -2386,7 +2394,7 @@ uvm_map_teardown(struct vm_map *map)
 		numq++;
 	KASSERT(numt == numq);
 #endif
-	uvm_unmap_detach(&dead_entries, 0);
+	uvm_unmap_detach(&dead_entries, waitable ? UVM_PLA_WAITOK : 0);
 	pmap_destroy(map->pmap);
 	map->pmap = NULL;
 }