move allocations between half a page and a page as close to the end of

the page as possible (i.e. make malloc option P a default).
ok art@ millert@ krw@

src/lib/libc/stdlib/malloc.3

@@ -30,9 +30,9 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: malloc.3,v 1.56 2008/11/02 14:42:01 otto Exp $
+.\"	$OpenBSD: malloc.3,v 1.57 2008/11/20 09:05:15 otto Exp $
 .\"
-.Dd $Mdocdate: November 2 2008 $
+.Dd $Mdocdate: November 20 2008 $
 .Dt MALLOC 3
 .Os
 .Sh NAME
@@ -254,6 +254,7 @@ Freed chunks are filled with 0xdf.
 Allocations larger than half a page but smaller that a page
 are aligned to the end of a page to catch buffer overruns in more
 cases.
+This is the default.
 .It Cm R
 .Dq realloc .
 Always reallocate when

src/lib/libc/stdlib/malloc.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.109 2008/11/20 09:01:24 otto Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.110 2008/11/20 09:05:15 otto Exp $	*/
 /*
  * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
  *
@@ -154,7 +154,7 @@ static int	malloc_active;		/* status of malloc */
 static int	malloc_freeprot;	/* mprotect free pages PROT_NONE? */
 static int	malloc_hint;		/* call madvice on free pages?  */
 static int	malloc_junk;		/* junk fill? */
-static int	malloc_move;		/* move allocations to end of page? */
+static int	malloc_move = 1;	/* move allocations to end of page? */
 static int	malloc_realloc;		/* always realloc? */
 static int	malloc_xmalloc;		/* xmalloc behaviour? */
 static int	malloc_zero;		/* zero fill? */