diff --git a/ChangeLog b/ChangeLog
index 9fb8816e..d46e5290 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -50,6 +50,7 @@
 - update C++/Python binding
 - oop, bool constants are always (int) now, so (^-1) works for unsigned types,
   thanks Nicolas
+- much lower memuse for im_cache() in complex pipelines
 
 12/5/10 started 7.22.2
 - the conditional image of ifthenelse can be any format, a (!=0) is added if
diff --git a/TODO b/TODO
index f7a15709..d05a00a9 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,6 @@
+
+
+
 - see Haida's mail re. cfitsio and higher dimensions
 
 
diff --git a/libvips/iofuncs/debug.c b/libvips/iofuncs/debug.c
index d9ed1fa0..57bedeef 100644
--- a/libvips/iofuncs/debug.c
+++ b/libvips/iofuncs/debug.c
@@ -229,16 +229,15 @@ im_demand_type im_char2dhint( const char *str )
 	{ return( char2enum( &enumdhint, str ) ); }
 
 static void *
-print_one_line_region( REGION *r, int *n2, gint64 *total )
+add_unique( REGION *r, gint64 *total, GSList **seen )
 {
-	if( r->type == IM_REGION_BUFFER && r->buffer ) {
-		printf( "\t*** %d) %zd malloced bytes\n", 
-			*n2, r->buffer->bsize );
+	if( r->type == IM_REGION_BUFFER && 
+		r->buffer &&
+		!g_slist_find( *seen, r->buffer ) ) {
+		*seen = g_slist_prepend( *seen, r->buffer );
 		*total += r->buffer->bsize;
 	}
 
-	*n2 += 1;
-
 	return( NULL );
 }
 
@@ -247,36 +246,37 @@ print_one_line_region( REGION *r, int *n2, gint64 *total )
 static void *
 print_one_line( IMAGE *im, int *n, gint64 *total )
 {
-	printf( "%2d) %p, %s, %s: %dx%d, %d bands, %s\n",
+	gint64 size;
+
+	printf( "%d, %p, %s, %s, %d, %d, %d, %s, ",
 		*n, 
 		im,
-		im_dtype2char( im->dtype ), im->filename, 
+		im_dtype2char( im->dtype ), 
+		im->filename, 
 		im->Xsize, im->Ysize, im->Bands,
 		im_BandFmt2char( im->BandFmt ) );
 	*n += 1;
 
+	size = 0;
 	if( im->dtype == IM_SETBUF && im->data ) {
-		gint64 size = (gint64) IM_IMAGE_SIZEOF_LINE( im ) * im->Ysize;
-
-		printf( "\t*** %" G_GINT64_FORMAT " malloced bytes\n", size );
-		*total += size;
+		size = (gint64) IM_IMAGE_SIZEOF_LINE( im ) * im->Ysize;
 	}
+	*total += size;
+	printf( "%" G_GINT64_FORMAT ", ", size );
 
+	printf( "%d, ", g_slist_length( im->regions ) );
+
+	size = 0;
 	if( im->regions ) {
-		int n2;
-		gint64 total2;
+		GSList *seen;
 
-		printf( "\t%d regions\n", g_slist_length( im->regions ) );
-
-		n2 = 0;
-		total2 = 0;
+		seen = NULL;
 		(void) im_slist_map2( im->regions, 
-			(VSListMap2Fn) print_one_line_region, &n2, &total2 );
-		if( total2 )
-			printf( "\t*** using total of %" G_GINT64_FORMAT 
-				" bytes\n", total2 );
-		*total += total2;
+			(VSListMap2Fn) add_unique, &size, &seen );
+		g_slist_free( seen );
 	}
+	*total += size;
+	printf( "%" G_GINT64_FORMAT "\n", size );
 
 	return( NULL );
 }
@@ -295,11 +295,13 @@ void
 im__print_all( void )
 {
 	if( im__open_images ) {
-		int n = 0;
-		gint64 total = 0;
+		int n;
+		gint64 total;
 
+		n = 0;
 		total = 0;
-		printf( "%d images\n", g_slist_length( im__open_images ) );
+		printf( "n, p, dtype, file, xsize, ysize, bands, fmt, " );
+		printf( "isize, nreg, rsize\n" );
 		(void) im_slist_map2( im__open_images, 
 			(VSListMap2Fn) print_one_line, &n, &total );
 		if( total )
diff --git a/libvips/iofuncs/sinkscreen.c b/libvips/iofuncs/sinkscreen.c
index 67f333a0..ebbd8e1a 100644
--- a/libvips/iofuncs/sinkscreen.c
+++ b/libvips/iofuncs/sinkscreen.c
@@ -2,6 +2,9 @@
  *
  * 1/1/10
  * 	- from im_render.c
+ * 25/11/10
+ * 	- in synchronous mode, use a single region for input and save huge 
+ * 	  mem use
  */
 
 /*
@@ -141,6 +144,11 @@ typedef struct _Render {
 	/* Hash of tiles with positions. Tiles can be dirty or painted.
 	 */
 	GHashTable *tiles;
+
+	/* In synchronous mode (notify == NULL), generate tiles with this 
+	 * REGION.
+	 */
+	REGION *synchronous_reg;
 } Render;
 
 /* Our per-thread state.
@@ -237,6 +245,7 @@ render_free( Render *render )
 	render->ntiles = 0;
 	IM_FREEF( g_slist_free, render->dirty );
 	IM_FREEF( g_hash_table_destroy, render->tiles );
+	IM_FREEF( im_region_free, render->synchronous_reg );
 
 	im_free( render );
 
@@ -615,6 +624,8 @@ render_new( VipsImage *in, VipsImage *out, VipsImage *mask,
 
 	render->tiles = g_hash_table_new( tile_hash, tile_equal ); 
 
+	render->synchronous_reg = NULL;
+
 	render->dirty = NULL;
 
 	/* Both out and mask must close before we can free the render.
@@ -635,6 +646,13 @@ render_new( VipsImage *in, VipsImage *out, VipsImage *mask,
 		render_ref( render );
 	}
 
+	/* In synchronous mode we need a region to generate pixels with.
+	 */
+	if( !notify ) {
+		if( !(render->synchronous_reg = im_region_create( in )) )
+			return( NULL );
+	}
+
 	VIPS_DEBUG_MSG_AMBER( "render_new: %p\n", render );
 
 #ifdef VIPS_DEBUG_AMBER
@@ -770,7 +788,8 @@ tile_queue( Tile *tile )
 			"painting tile %p %dx%d synchronously\n",
 			tile, tile->area.left, tile->area.top );
 
-		if( im_prepare( tile->region, &tile->area ) )
+		if( im_prepare_to( render->synchronous_reg, tile->region, 
+			&tile->area, tile->area.left, tile->area.top ) ) 
 			VIPS_DEBUG_MSG_RED( "tile_queue: prepare failed\n" ); 
 
 		tile->painted = TRUE;