Define a new flag, UVM_FLAG_HOLE, for uvm_map to create a vm_map_entry of

a new etype, UVM_ET_HOLE, meaning it has no backend.

UVM_ET_HOLE entries (which should be created as UVM_PROT_NONE and with
UVM_FLAG_NOMERGE and UVM_FLAG_HOLE) are skipped in uvm_unmap_remove(), so
that pmap_{k,}remove() is not called on the entry.

This is intended to save time, and behave better, on pmaps with MMU holes
at process exit time.

ok art@, kettenis@ provided feedback as well.

5 files changed, 21 insertions, 10 deletions

diff --git a/share/man/man9/uvm.9 b/share/man/man9/uvm.9
index 3adb7515243..2381fc24b87 100644
--- a/share/man/man9/uvm.9
+++ b/share/man/man9/uvm.9
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: uvm.9,v 1.34 2008/05/06 16:26:07 jmc Exp $
+.\"	$OpenBSD: uvm.9,v 1.35 2008/06/09 20:30:22 miod Exp $
 .\"	$NetBSD: uvm.9,v 1.14 2000/06/29 06:08:44 mrg Exp $
 .\"
 .\" Copyright (c) 1998 Matthew R. Green
@@ -30,7 +30,7 @@
 .\" XXX this manual sets nS to 1 or 0 in the description, to obtain
 .\" synopsis-like function prototypes.  any better way?
 .\"
-.Dd $Mdocdate: May 6 2008 $
+.Dd $Mdocdate: June 9 2008 $
 .Dt UVM 9
 .Os
 .Sh NAME
@@ -257,6 +257,7 @@ can take are:
 #define UVM_FLAG_COPYONW 0x080000 /* set copy_on_write flag */
 #define UVM_FLAG_AMAPPAD 0x100000 /* bss: pad amap to reduce malloc() */
 #define UVM_FLAG_TRYLOCK 0x200000 /* fail if we can not lock map */
+#define UVM_FLAG_HOLE    0x400000 /* no backend */
 .Ed
 .Pp
 The
diff --git a/sys/uvm/uvm.h b/sys/uvm/uvm.h
index 977d45c3b29..3d04e53b9a4 100644
--- a/sys/uvm/uvm.h
+++ b/sys/uvm/uvm.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm.h,v 1.23 2008/05/05 15:37:41 thib Exp $	*/
+/*	$OpenBSD: uvm.h,v 1.24 2008/06/09 20:30:23 miod Exp $	*/
 /*	$NetBSD: uvm.h,v 1.24 2000/11/27 08:40:02 chs Exp $	*/
 
 /*
@@ -128,11 +128,13 @@ struct uvm {
 #define UVM_ET_SUBMAP		0x02	/* it is a vm_map submap */
 #define UVM_ET_COPYONWRITE 	0x04	/* copy_on_write */
 #define UVM_ET_NEEDSCOPY	0x08	/* needs_copy */
+#define	UVM_ET_HOLE		0x10	/* no backend */
 
 #define UVM_ET_ISOBJ(E)		(((E)->etype & UVM_ET_OBJ) != 0)
 #define UVM_ET_ISSUBMAP(E)	(((E)->etype & UVM_ET_SUBMAP) != 0)
 #define UVM_ET_ISCOPYONWRITE(E)	(((E)->etype & UVM_ET_COPYONWRITE) != 0)
 #define UVM_ET_ISNEEDSCOPY(E)	(((E)->etype & UVM_ET_NEEDSCOPY) != 0)
+#define UVM_ET_ISHOLE(E)	(((E)->etype & UVM_ET_HOLE) != 0)
 
 #ifdef _KERNEL
 
diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
index 406a2a0391c..f0e48816b5b 100644
--- a/sys/uvm/uvm_extern.h
+++ b/sys/uvm/uvm_extern.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_extern.h,v 1.69 2008/04/09 16:58:11 deraadt Exp $	*/
+/*	$OpenBSD: uvm_extern.h,v 1.70 2008/06/09 20:30:23 miod Exp $	*/
 /*	$NetBSD: uvm_extern.h,v 1.57 2001/03/09 01:02:12 chs Exp $	*/
 
 /*
@@ -184,6 +184,7 @@ typedef int		vm_prot_t;
 #define UVM_FLAG_COPYONW 0x080000 /* set copy_on_write flag */
 #define UVM_FLAG_AMAPPAD 0x100000 /* for bss: pad amap to reduce malloc() */
 #define UVM_FLAG_TRYLOCK 0x200000 /* fail if we can not lock map */
+#define	UVM_FLAG_HOLE    0x400000 /* no backend */
 
 /* macros to extract info */
 #define UVM_PROTECTION(X)	((X) & UVM_PROT_MASK)
diff --git a/sys/uvm/uvm_map.c b/sys/uvm/uvm_map.c
index bc605570b0d..a13a7ce92a6 100644
--- a/sys/uvm/uvm_map.c
+++ b/sys/uvm/uvm_map.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.c,v 1.99 2007/09/15 10:10:37 martin Exp $	*/
+/*	$OpenBSD: uvm_map.c,v 1.100 2008/06/09 20:30:23 miod Exp $	*/
 /*	$NetBSD: uvm_map.c,v 1.86 2000/11/27 08:40:03 chs Exp $	*/
 
 /* 
@@ -897,6 +897,8 @@ step3:
 		if ((flags & UVM_FLAG_OVERLAY) == 0)
 			new_entry->etype |= UVM_ET_NEEDSCOPY;
 	}
+	if (flags & UVM_FLAG_HOLE)
+		new_entry->etype |= UVM_ET_HOLE;
 
 	new_entry->protection = prot;
 	new_entry->max_protection = maxprot;
@@ -1451,7 +1453,9 @@ uvm_unmap_remove(struct vm_map *map, vaddr_t start, vaddr_t end,
 		 * special case: handle mappings to anonymous kernel objects.
 		 * we want to free these pages right away...
 		 */
-		if (map->flags & VM_MAP_INTRSAFE) {
+		if (UVM_ET_ISHOLE(entry)) {
+			/* nothing to do! */
+		} else if (map->flags & VM_MAP_INTRSAFE) {
 			uvm_km_pgremove_intrsafe(entry->start, entry->end);
 			pmap_kremove(entry->start, len);
 		} else if (UVM_ET_ISOBJ(entry) &&
diff --git a/usr.sbin/procmap/procmap.c b/usr.sbin/procmap/procmap.c
index fc0cad510d6..2140d7423ba 100644
--- a/usr.sbin/procmap/procmap.c
+++ b/usr.sbin/procmap/procmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: procmap.c,v 1.27 2007/10/02 14:50:49 kettenis Exp $ */
+/*	$OpenBSD: procmap.c,v 1.28 2008/06/09 20:30:25 miod Exp $ */
 /*	$NetBSD: pmap.c,v 1.1 2002/09/01 20:32:44 atatat Exp $ */
 
 /*
@@ -552,11 +552,12 @@ dump_vm_map_entry(kvm_t *kd, struct kbit *vmspace,
 		printf(" end = %lx,", vme->end);
 		printf(" object.uvm_obj/sub_map = %p,\n", vme->object.uvm_obj);
 		printf("    offset = %lx,", (unsigned long)vme->offset);
-		printf(" etype = %x <%s%s%s%s >,", vme->etype,
+		printf(" etype = %x <%s%s%s%s%s >,", vme->etype,
 		    vme->etype & UVM_ET_OBJ ? " OBJ" : "",
 		    vme->etype & UVM_ET_SUBMAP ? " SUBMAP" : "",
 		    vme->etype & UVM_ET_COPYONWRITE ? " COW" : "",
-		    vme->etype & UVM_ET_NEEDSCOPY ? " NEEDSCOPY" : "");
+		    vme->etype & UVM_ET_NEEDSCOPY ? " NEEDSCOPY" : "",
+		    vme->etype & UVM_ET_HOLE ? " HOLE" : "");
 		printf(" protection = %x,\n", vme->protection);
 		printf("    max_protection = %x,", vme->max_protection);
 		printf(" inheritance = %d,", vme->inheritance);
@@ -811,7 +812,9 @@ findname(kvm_t *kd, struct kbit *vmspace,
 	    D(vmspace, vmspace)->vm_dsize * getpagesize() / 2 <
 	    (vme->end - vme->start)) {
 		name = "  [ heap ]";
-	} else
+	} else if (UVM_ET_ISHOLE(vme))
+		name = "  [ hole ]";
+	else
 		name = "  [ anon ]";
 
 	return (name);