Index: usr.sbin/sysinst/bsddisklabel.c
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/bsddisklabel.c,v
retrieving revision 1.33
diff -u -p -r1.33 bsddisklabel.c
--- usr.sbin/sysinst/bsddisklabel.c	13 Dec 2019 22:12:41 -0000	1.33
+++ usr.sbin/sysinst/bsddisklabel.c	18 Dec 2019 09:57:03 -0000
@@ -137,10 +137,18 @@ default_parts_init[] =
 #endif
 	  .type = PT_swap, .fs_type = FS_SWAP },
 #ifdef HAVE_TMPFS
-	{ .type = PT_root, .mount = "/tmp", .fs_type = FS_TMPFS,
+	{
+#if DEFTMPSIZE > 0
+	  .size = DEFTMPSIZE*(MEG/512),
+#endif
+	  .type = PT_root, .mount = "/tmp", .fs_type = FS_TMPFS,
 	  .flags = PUIFLG_JUST_MOUNTPOINT },
 #else
-	{ .type = PT_root, .mount = "/tmp", .fs_type = FS_MFS,
+	{
+#if DEFTMPSIZE > 0
+	  .size = DEFTMPSIZE*(MEG/512),
+#endif
+	  .type = PT_root, .mount = "/tmp", .fs_type = FS_MFS,
 	  .flags = PUIFLG_JUST_MOUNTPOINT },
 #endif
 	{ .def_size = DEFUSRSIZE*(MEG/512), .mount = "/usr", .type = PT_root },
@@ -891,6 +899,13 @@ fill_defaults(struct partition_usage_set
 		if (wanted->infos[i].type == PT_swap)
 			wanted->infos[i].size = get_ramsize() * (MEG / 512);
 #endif
+#if DEFTMPSIZE == -1
+		if (wanted->infos[i].type == PT_swap)
+			wanted->infos[i].size = get_ramsize() *
+			    (MEG / DEFTMPFRAC);
+#endif
+
+
 		if (wanted->infos[i].type == PT_swap && swap > wanted->num)
 			swap = i;
 #if defined(DEFAULT_UFS2) && !defined(HAVE_UFS2_BOOT)
Index: usr.sbin/sysinst/defsizes.h
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/defsizes.h,v
retrieving revision 1.4
diff -u -p -r1.4 defsizes.h
--- usr.sbin/sysinst/defsizes.h	12 Jun 2019 06:20:17 -0000	1.4
+++ usr.sbin/sysinst/defsizes.h	18 Dec 2019 09:57:03 -0000
@@ -54,6 +54,9 @@
 #ifndef	DEBNEEDMB
 #define	DEBNEEDMB	800
 #endif
+#ifndef DEFTMPSIZE
+#define DEFTMPSIZE	0
+#endif
 
 #ifndef MD_SETS_SELECTED
 #define MD_SETS_SELECTED SET_KERNEL_1, SET_SYSTEM, SET_X11, SET_MD
Index: usr.sbin/sysinst/arch/alpha/md.h
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/arch/alpha/md.h,v
retrieving revision 1.2
diff -u -p -r1.2 md.h
--- usr.sbin/sysinst/arch/alpha/md.h	16 Nov 2018 19:54:03 -0000	1.2
+++ usr.sbin/sysinst/arch/alpha/md.h	18 Dec 2019 09:57:03 -0000
@@ -49,6 +49,8 @@
 #define DEFROOTSIZE	128
 #define	DEFUSRSIZE	900
 #define	DEBNEEDMB	1024
+#define	DEFTMPSIZE	(-1)
+#define	DEFTMPFRAC	4	/* 1/4 of RAM size */
 
 /* have support for booting from UFS2 */
 #define	HAVE_UFS2_BOOT
Index: usr.sbin/sysinst/arch/amd64/md.h
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/arch/amd64/md.h,v
retrieving revision 1.8
diff -u -p -r1.8 md.h
--- usr.sbin/sysinst/arch/amd64/md.h	16 Nov 2019 21:25:14 -0000	1.8
+++ usr.sbin/sysinst/arch/amd64/md.h	18 Dec 2019 09:57:03 -0000
@@ -53,6 +53,9 @@
 
 #define	DEFSWAPSIZE	(-1)
 
+#define	DEFTMPSIZE	(-1)
+#define	DEFTMPFRAC	4	/* 1/4 of RAM size */
+
 /* use UFS2 by default for ffs */
 #define	DEFAULT_UFS2
 
Index: usr.sbin/sysinst/arch/i386/md.h
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/arch/i386/md.h,v
retrieving revision 1.7
diff -u -p -r1.7 md.h
--- usr.sbin/sysinst/arch/i386/md.h	2 Oct 2019 11:16:02 -0000	1.7
+++ usr.sbin/sysinst/arch/i386/md.h	18 Dec 2019 09:57:03 -0000
@@ -49,6 +49,8 @@
 #define	DEFUSRSIZE	0
 #define	DEFSWAPSIZE	(-1)
 #define	DEFROOTSIZE	90
+#define	DEFTMPSIZE	(-1)
+#define	DEFTMPFRAC	4	/* 1/4 of RAM size */
 
 /* Megs required for a full X installation. */
 #define XNEEDMB 250
Index: usr.sbin/sysinst/arch/sparc64/md.h
===================================================================
RCS file: /cvsroot/src/usr.sbin/sysinst/arch/sparc64/md.h,v
retrieving revision 1.5
diff -u -p -r1.5 md.h
--- usr.sbin/sysinst/arch/sparc64/md.h	20 Jun 2019 18:32:33 -0000	1.5
+++ usr.sbin/sysinst/arch/sparc64/md.h	18 Dec 2019 09:57:03 -0000
@@ -51,6 +51,9 @@
 #define DEFROOTSIZE	64	/* Default root size */
 #define DEFVARSIZE	32	/* Default /var size, if created */
 #define DEFUSRSIZE	1200	/* Default /usr size, if /home */
+#define	DEFTMPSIZE	(-1)
+#define	DEFTMPFRAC	4	/* 1/4 of RAM size */
+
 #define XNEEDMB		300	/* Extra megs for full X installation */
 #define DEBNEEDMB	1200	/* Extra megs for debug sets */