add a threaded tile cache

seems to work!

libvips/conversion/Makefile.am

@@ -1,6 +1,7 @@
 noinst_LTLIBRARIES = libconversion.la
 
 libconversion_la_SOURCES = \
+	threadcache.c \
 	conversion.c \
 	conversion.h \
 	tilecache.c \

libvips/conversion/conversion.c

@@ -123,6 +123,7 @@ vips_conversion_operation_init( void )
 	extern GType vips_recomb_get_type( void ); 
 	extern GType vips_bandmean_get_type( void ); 
 	extern GType vips_flatten_get_type( void ); 
+	extern GType vips_thread_cache_get_type( void ); 
 
 	vips_copy_get_type();
 	vips_tile_cache_get_type(); 
@@ -144,6 +145,7 @@ vips_conversion_operation_init( void )
 	vips_recomb_get_type(); 
 	vips_bandmean_get_type(); 
 	vips_flatten_get_type(); 
+	vips_thread_cache_get_type(); 
 }
 
 /* The common part of most binary conversion

libvips/conversion/threadcache.c

@@ -0,0 +1,702 @@
+/* Threaded tile cache
+ *
+ * A tile cache with threaded access. Manty readers coordinate tile
+ * calculation. 
+ *
+ * 8/10/12
+ * 	- from tilecache
+ */
+
+/*
+
+    This file is part of VIPS.
+    
+    VIPS is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a cache of the GNU Lesser General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+/*
+#define VIPS_DEBUG
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif /*HAVE_CONFIG_H*/
+#include <vips/intl.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <vips/vips.h>
+#include <vips/internal.h>
+#include <vips/debug.h>
+
+#include "conversion.h"
+
+/* A tile in cache can be in one of three states:
+ *
+ * DATA		- the tile holds valid pixels 
+ * CALC		- some thread somewhere is calculating it
+ * PEND		- some thread somewhere wants it
+ */
+typedef enum VipsTileState {
+	VIPS_TILE_STATE_DATA,
+	VIPS_TILE_STATE_CALC,
+	VIPS_TILE_STATE_PEND
+} VipsTileState;
+
+/* A tile in our cache.
+ */
+typedef struct _VipsTile {
+	struct _VipsThreadCache *cache;
+
+	VipsTileState state;
+
+	/* We count how many threads are relying on this tile. This tile can't
+	 * be flushed if ref_count > 0.
+	 */
+	int ref_count; 
+
+	VipsRegion *region;		/* Region with private mem for data */
+
+	/* Tile position. Just use left/top to calculate a hash. This is the
+	 * key for the hash table. Don't use region->valid in case the region
+	 * pointer is NULL.
+	 */
+	VipsRect pos; 
+
+	int time;			/* Time of last use for LRU */
+} VipsTile;
+
+typedef struct _VipsThreadCache {
+	VipsConversion parent_instance;
+
+	VipsImage *in;
+	int tile_width;	
+	int tile_height;
+	int max_tiles;
+	VipsCacheStrategy strategy;
+
+	int time;			/* Update ticks for LRU here */
+	int ntiles;			/* Current cache size */
+	GMutex *lock;			/* Lock everything here */
+	GCond *new_tile;		/* A new tile is ready */
+	GHashTable *tiles;		/* Tiles, hashed by coordinates */
+} VipsThreadCache;
+
+typedef VipsConversionClass VipsThreadCacheClass;
+
+G_DEFINE_TYPE( VipsThreadCache, vips_thread_cache, VIPS_TYPE_CONVERSION );
+
+#define VIPS_TYPE_THREAD_CACHE (vips_thread_cache_get_type())
+
+static void
+vips_thread_cache_drop_all( VipsThreadCache *cache )
+{
+	g_hash_table_remove_all( cache->tiles ); 
+}
+
+static void
+vips_thread_cache_dispose( GObject *gobject )
+{
+	VipsThreadCache *cache = (VipsThreadCache *) gobject;
+
+	vips_thread_cache_drop_all( cache );
+	VIPS_FREEF( g_mutex_free, cache->lock );
+	VIPS_FREEF( g_cond_free, cache->new_tile );
+
+	G_OBJECT_CLASS( vips_thread_cache_parent_class )->dispose( gobject );
+}
+
+static int
+vips_tile_move( VipsTile *tile, int x, int y )
+{
+	/* We are changing x/y and therefore the hash value. We must unlink
+	 * from the old hash position and relink at the new place.
+	 */
+	g_hash_table_steal( tile->cache->tiles, &tile->pos );
+
+	tile->pos.left = x;
+	tile->pos.top = y;
+	tile->pos.width = tile->cache->tile_width;
+	tile->pos.height = tile->cache->tile_height;
+
+	g_hash_table_insert( tile->cache->tiles, &tile->pos, tile );
+
+	if( vips_region_buffer( tile->region, &tile->pos ) )
+		return( -1 );
+
+	/* No data yet, but someone must want it.
+	 */
+	tile->state = VIPS_TILE_STATE_PEND;
+
+	return( 0 );
+}
+
+static VipsTile *
+vips_tile_new( VipsThreadCache *cache, int x, int y )
+{
+	VipsTile *tile;
+
+	if( !(tile = VIPS_NEW( NULL, VipsTile )) )
+		return( NULL );
+
+	tile->cache = cache;
+	tile->state = VIPS_TILE_STATE_PEND;
+	tile->ref_count = 0;
+	tile->region = NULL;
+	tile->time = cache->time;
+	tile->pos.left = x;
+	tile->pos.top = y;
+	tile->pos.width = cache->tile_width;
+	tile->pos.height = cache->tile_height;
+	g_hash_table_insert( cache->tiles, &tile->pos, tile );
+	g_assert( cache->ntiles >= 0 );
+	cache->ntiles += 1;
+
+	if( !(tile->region = vips_region_new( cache->in )) ) {
+		g_hash_table_remove( cache->tiles, &tile->pos );
+		return( NULL );
+	}
+
+	vips__region_no_ownership( tile->region );
+
+	if( vips_tile_move( tile, x, y ) ) {
+		g_hash_table_remove( cache->tiles, &tile->pos );
+		return( NULL );
+	}
+
+	return( tile );
+}
+
+/* Do we have a tile in the cache?
+ */
+static VipsTile *
+vips_tile_search( VipsThreadCache *cache, int x, int y )
+{
+	VipsRect pos;
+	VipsTile *tile;
+
+	pos.left = x;
+	pos.top = y;
+	pos.width = cache->tile_width;
+	pos.height = cache->tile_height;
+	tile = (VipsTile *) g_hash_table_lookup( cache->tiles, &pos );
+
+	return( tile );
+}
+
+static void
+vips_tile_touch( VipsTile *tile )
+{
+	g_assert( tile->cache->ntiles >= 0 );
+
+	tile->time = tile->cache->time++;
+}
+
+/* Fill a tile with pixels.
+ */
+static int
+vips_tile_fill( VipsTile *tile, VipsRegion *in )
+{
+	VIPS_DEBUG_MSG( "tilecache: filling tile %d x %d\n", 
+		tile->pos.left, tile->pos.top );
+
+	if( vips_region_prepare_to( in, tile->region, 
+		&tile->pos, tile->pos.left, tile->pos.top ) ) 
+		return( -1 );
+	tile->state = VIPS_TILE_STATE_DATA;
+
+	vips_tile_touch( tile );
+
+	return( 0 );
+}
+
+typedef struct _VipsTileSearch {
+	VipsTile *tile;
+
+	int oldest;
+	int topmost;
+} VipsTileSearch;
+
+static void 
+vips_tile_oldest( gpointer key, gpointer value, gpointer user_data )
+{
+	VipsTile *tile = (VipsTile *) value;
+	VipsTileSearch *search = (VipsTileSearch *) user_data;
+
+	/* Only consider unreffed tiles for recycling.
+	 */
+	if( !tile->ref_count &&
+		tile->time < search->oldest ) {
+		search->oldest = tile->time;
+		search->tile = tile;
+	}
+}
+
+static void 
+vips_tile_topmost( gpointer key, gpointer value, gpointer user_data )
+{
+	VipsTile *tile = (VipsTile *) value;
+	VipsTileSearch *search = (VipsTileSearch *) user_data;
+
+	/* Only consider unreffed tiles for recycling.
+	 */
+	if( !tile->ref_count &&
+		tile->pos.top < search->topmost ) {
+		search->topmost = tile->pos.top;
+		search->tile = tile;
+	}
+}
+
+/* Find existing tile, make a new tile, or if we have a full set of tiles, 
+ * reuse a tile.
+ */
+static VipsTile *
+vips_tile_find( VipsThreadCache *cache, int x, int y )
+{
+	VipsTile *tile;
+	VipsTileSearch search;
+
+	/* In cache already?
+	 */
+	if( (tile = vips_tile_search( cache, x, y )) ) {
+		vips_tile_touch( tile );
+
+		return( tile );
+	}
+
+	/* VipsThreadCache not full? Make a new tile.
+	 */
+	if( cache->max_tiles == -1 ||
+		cache->ntiles < cache->max_tiles ) {
+		if( !(tile = vips_tile_new( cache, x, y )) )
+			return( NULL );
+
+		return( tile );
+	}
+
+	/* Reuse an old one.
+	 */
+	switch( cache->strategy ) {
+	case VIPS_CACHE_RANDOM:
+		search.oldest = cache->time;
+		search.tile = NULL;
+		g_hash_table_foreach( cache->tiles, 
+			vips_tile_oldest, &search );
+		tile = search.tile; 
+		break;
+
+	case VIPS_CACHE_SEQUENTIAL:
+		search.topmost = cache->in->Ysize;
+		search.tile = NULL;
+		g_hash_table_foreach( cache->tiles, 
+			vips_tile_topmost, &search );
+		tile = search.tile; 
+		break;
+
+	default:
+		g_assert( 0 );
+	}
+
+	if( !tile ) {
+		/* There are no tiles we can reuse -- we have to make another
+		 * for now. They will get culled down again next time around.
+		 */
+		if( !(tile = vips_tile_new( cache, x, y )) ) 
+			return( NULL );
+
+		return( tile );
+	}
+
+	VIPS_DEBUG_MSG( "tilecache: reusing tile %d x %d\n", 
+		tile->pos.left, tile->pos.top );
+
+	if( vips_tile_move( tile, x, y ) )
+		return( NULL );
+
+	return( tile );
+}
+
+static gboolean            
+vips_tile_unlocked( gpointer key, gpointer value, gpointer user_data )
+{
+	VipsTile *tile = (VipsTile *) value;
+
+	return( !tile->ref_count );
+}
+
+static void
+vips_thread_cache_minimise( VipsImage *image, VipsThreadCache *cache )
+{
+	/* We can't drop tiles that are in use.
+	 */
+	g_mutex_lock( cache->lock );
+
+	g_hash_table_foreach_remove( cache->tiles, 
+		vips_tile_unlocked, NULL );
+
+	g_mutex_unlock( cache->lock );
+}
+
+static void
+vips_thread_cache_unref( GSList *work )
+{
+	GSList *p;
+
+	for( p = work; p; p = p->next ) { 
+		VipsTile *tile = (VipsTile *) p->data;
+
+		tile->ref_count -= 1;
+	}
+
+	g_slist_free( work );
+}
+
+/* Make a set of work tiles.
+ */
+static GSList *
+vips_thread_cache_ref( VipsThreadCache *cache, VipsRect *r )
+{
+	const int tw = cache->tile_width;
+	const int th = cache->tile_height;
+
+	/* Find top left of tiles we need.
+	 */
+	const int xs = (r->left / tw) * tw;
+	const int ys = (r->top / th) * th;
+
+	GSList *work;
+	VipsTile *tile;
+	int x, y;
+
+	/* Ref all the tiles we will need.
+	 */
+	work = NULL;
+	for( y = ys; y < VIPS_RECT_BOTTOM( r ); y += th )
+		for( x = xs; x < VIPS_RECT_RIGHT( r ); x += tw ) {
+			if( !(tile = vips_tile_find( cache, x, y )) ) {
+				vips_thread_cache_unref( work );
+				return( NULL );
+			}
+
+			tile->ref_count += 1;
+			work = g_slist_prepend( work, tile );
+
+			VIPS_DEBUG_MSG( "vips_thread_cache_gen: "
+				"tile %d, %d (%p)\n", x, y, tile ); 
+		}
+
+	return( work );
+}
+
+static void
+vips_tile_paste( VipsTile *tile, VipsRegion *or )
+{
+	VipsRect hit;
+
+	/* The part of the tile that we need.
+	 */
+	vips_rect_intersectrect( &or->valid, &tile->pos, &hit );
+	if( !vips_rect_isempty( &hit ) )
+		vips_region_copy( tile->region, or, &hit, hit.left, hit.top ); 
+}
+
+static int
+vips_thread_cache_gen( VipsRegion *or, 
+	void *seq, void *a, void *b, gboolean *stop )
+{
+	VipsRegion *in = (VipsRegion *) seq;
+	VipsThreadCache *cache = (VipsThreadCache *) b;
+	VipsRect *r = &or->valid;
+
+	VipsTile *tile;
+	GSList *work;
+	GSList *p;
+
+	g_mutex_lock( cache->lock );
+
+	VIPS_DEBUG_MSG( "vips_thread_cache_gen: "
+		"left = %d, top = %d, width = %d, height = %d\n",
+		r->left, r->top, r->width, r->height );
+
+	/* Ref all the tiles we will need.
+	 */
+	work = vips_thread_cache_ref( cache, r );
+
+	while( work ) {
+		/* Search for data tiles: easy, we can just paste those in.
+		 */
+		for(;;) { 
+			for( p = work; p; p = p->next ) { 
+				tile = (VipsTile *) p->data;
+
+				if( tile->state == VIPS_TILE_STATE_DATA ) 
+					break;
+			}
+
+			if( !p )
+				break;
+			
+			VIPS_DEBUG_MSG( "vips_thread_cache_gen: "
+					"pasting %p\n", tile ); 
+
+			vips_tile_paste( tile, or );
+
+			/* We're done with this tile.
+			 */
+			work = g_slist_remove( work, tile );
+			tile->ref_count -= 1;
+		}
+
+		/* Now search for PEND tiles, we can calculate them. 
+		 */
+		for( p = work; p; p = p->next ) { 
+			tile = (VipsTile *) p->data;
+
+			if( tile->state == VIPS_TILE_STATE_PEND ) {
+				/* Calculate this tile. Other threads can use 
+				 * the cache while we calculate pixels.
+				 */
+				tile->state = VIPS_TILE_STATE_CALC;
+
+				VIPS_DEBUG_MSG( "vips_thread_cache_gen: "
+					"calc of %p\n", tile ); 
+
+				g_mutex_unlock( cache->lock );
+
+				if( vips_tile_fill( tile, in ) ) {
+					vips_thread_cache_unref( work );
+					return( -1 );
+				}
+
+				g_mutex_lock( cache->lock );
+
+				/* Let everyone know there's a new DATA tile. 
+				 * They need to all check their work lists.
+				 */
+				g_cond_broadcast( cache->new_tile );
+
+				break;
+			}
+		}
+
+		if( !p && 
+			work ) {
+			VIPS_DEBUG_MSG( "vips_thread_cache_gen: waiting\n" ); 
+
+			/* All the tiles we need are being calculated. We 
+			 * must block on the new-tile cond, then try again.
+			 */
+			g_cond_wait( cache->new_tile, cache->lock );
+
+			VIPS_DEBUG_MSG( "vips_thread_cache_gen: awake!\n" ); 
+		}
+	}
+
+	g_mutex_unlock( cache->lock );
+
+	return( 0 );
+}
+
+static int
+vips_thread_cache_build( VipsObject *object )
+{
+	VipsConversion *conversion = VIPS_CONVERSION( object );
+	VipsThreadCache *cache = (VipsThreadCache *) object;
+
+	VIPS_DEBUG_MSG( "vips_thread_cache_build\n" );
+
+	if( VIPS_OBJECT_CLASS( vips_thread_cache_parent_class )->
+		build( object ) )
+		return( -1 );
+
+	g_signal_connect( conversion->out, "minimise", 
+		G_CALLBACK( vips_thread_cache_minimise ), cache );
+
+	if( vips_image_pio_input( cache->in ) )
+		return( -1 );
+
+	if( vips_image_copy_fields( conversion->out, cache->in ) )
+		return( -1 );
+        vips_demand_hint( conversion->out, 
+		VIPS_DEMAND_STYLE_SMALLTILE, cache->in, NULL );
+
+	if( vips_image_generate( conversion->out,
+		vips_start_one, vips_thread_cache_gen, vips_stop_one, 
+		cache->in, cache ) )
+		return( -1 );
+
+	return( 0 );
+}
+
+static void
+vips_thread_cache_class_init( VipsThreadCacheClass *class )
+{
+	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
+	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+
+	VIPS_DEBUG_MSG( "vips_thread_cache_class_init\n" );
+
+	gobject_class->dispose = vips_thread_cache_dispose;
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	vobject_class->nickname = "threadcache";
+	vobject_class->description = _( "cache an image" );
+	vobject_class->build = vips_thread_cache_build;
+
+	VIPS_ARG_IMAGE( class, "in", 1, 
+		_( "Input" ), 
+		_( "Input image" ),
+		VIPS_ARGUMENT_REQUIRED_INPUT,
+		G_STRUCT_OFFSET( VipsThreadCache, in ) );
+
+	VIPS_ARG_INT( class, "tile_width", 2, 
+		_( "Tile width" ), 
+		_( "Tile width in pixels" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThreadCache, tile_width ),
+		1, 1000000, 128 );
+
+	VIPS_ARG_INT( class, "tile_height", 3, 
+		_( "Tile height" ), 
+		_( "Tile height in pixels" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThreadCache, tile_height ),
+		1, 1000000, 128 );
+
+	VIPS_ARG_ENUM( class, "strategy", 4, 
+		_( "Strategy" ), 
+		_( "Expected access pattern" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThreadCache, strategy ),
+		VIPS_TYPE_CACHE_STRATEGY, VIPS_CACHE_RANDOM );
+
+	VIPS_ARG_INT( class, "max_tiles", 5, 
+		_( "Max tiles" ), 
+		_( "Maximum number of tiles to cache" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThreadCache, max_tiles ),
+		-1, 1000000, 1000 );
+}
+
+static unsigned int
+vips_rect_hash( VipsRect *pos )
+{
+	guint hash;
+
+	/* We could shift down by the tile size?
+	 */
+	hash = pos->left ^ (pos->top << 16);
+
+	return( hash );
+}
+
+static gboolean 
+vips_rect_equal( VipsRect *a, VipsRect *b )
+{
+	return( a->left == b->left && a->top == b->top );
+}
+
+static void
+vips_tile_destroy( VipsTile *tile )
+{
+	VipsThreadCache *cache = tile->cache;
+
+	cache->ntiles -= 1;
+	g_assert( cache->ntiles >= 0 );
+	tile->cache = NULL;
+
+	VIPS_UNREF( tile->region );
+
+	vips_free( tile );
+}
+
+static void
+vips_thread_cache_init( VipsThreadCache *cache )
+{
+	cache->tile_width = 128;
+	cache->tile_height = 128;
+	cache->max_tiles = 1000;
+	cache->strategy = VIPS_CACHE_RANDOM;
+
+	cache->time = 0;
+	cache->ntiles = 0;
+	cache->lock = g_mutex_new();
+	cache->new_tile = g_cond_new();
+	cache->tiles = g_hash_table_new_full( 
+		(GHashFunc) vips_rect_hash, 
+		(GEqualFunc) vips_rect_equal,
+		NULL,
+		(GDestroyNotify) vips_tile_destroy );
+}
+
+/**
+ * vips_threadcache:
+ * @in: input image
+ * @out: output image
+ * @...: %NULL-terminated list of optional named arguments
+ *
+ * Optional arguments:
+ *
+ * @tile_width: width of tiles in cache
+ * @tile_height: height of tiles in cache
+ * @strategy: hint expected access pattern #VipsCacheStrategy
+ * @max_tiles: maximum number of tiles to cache
+ *
+ * This operation behaves rather like vips_copy() between images
+ * @in and @out, except that it keeps a cache of computed pixels. 
+ * This cache is made of up to @max_tiles tiles (a value of -1 
+ * means any number of tiles), and each tile is of size @tile_width
+ * by @tile_height pixels. 
+ *
+ * Each cache tile is made with a single call to 
+ * vips_image_prepare(). 
+ *
+ * When the cache fills, a tile is chosen for reuse. If @strategy is
+ * #VIPS_CACHE_RANDOM, then the least-recently-used tile is reused. If 
+ * @strategy is #VIPS_CACHE_SEQUENTIAL, the top-most tile is reused.
+ *
+ * By default, @tile_width and @tile_height are 128 pixels, and the operation
+ * will cache up to 1,000 tiles. @strategy defaults to #VIPS_CACHE_RANDOM.
+ *
+ * Unlike vips_tilecache(), this operation does not single-thread it's callee.
+ * Many tile requests can happen in parallel, and vips_threadcache()
+ * coordinates them to prevent recomputation.
+ *
+ * See also: vips_cache(), vips_linecache().
+ *
+ * Returns: 0 on success, -1 on error.
+ */
+int
+vips_threadcache( VipsImage *in, VipsImage **out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "threadcache", ap, in, out );
+	va_end( ap );
+
+	return( result );
+}

libvips/conversion/tilecache.c

@@ -226,7 +226,7 @@ typedef struct _VipsTileSearch {
 	int topmost;
 } VipsTileSearch;
 
-void 
+static void 
 vips_tile_oldest( gpointer key, gpointer value, gpointer user_data )
 {
 	VipsTile *tile = (VipsTile *) value;
@@ -238,7 +238,7 @@ vips_tile_oldest( gpointer key, gpointer value, gpointer user_data )
 	}
 }
 
-void 
+static void 
 vips_tile_topmost( gpointer key, gpointer value, gpointer user_data )
 {
 	VipsTile *tile = (VipsTile *) value;

libvips/foreign/openslide2vips.c

@@ -399,19 +399,17 @@ vips__openslide_read( const char *filename, VipsImage *out, int level )
 	/* Tile cache: keep enough for two complete rows of tiles. OpenSlide
 	 * has its own tile cache, but it's not large enough for a complete
 	 * scan line.
+	 */
 	VipsImage *raw;
 	VipsImage *t;
+
 	raw = vips_image_new();
 	vips_object_local( out, raw );
 
 	if( !(rslide = readslide_new( filename, raw, level, NULL )) )
 		return( -1 );
-	 */
 
-	if( !(rslide = readslide_new( filename, out, level, NULL )) )
-		return( -1 );
-
-	if( vips_image_generate( out, 
+	if( vips_image_generate( raw, 
 		vips__openslide_start, 
 		vips__openslide_generate, 
 		vips__openslide_stop, 
@@ -420,9 +418,10 @@ vips__openslide_read( const char *filename, VipsImage *out, int level )
 
 	/* Copy to out, adding a cache. Enough tiles for a complete row, plus
 	 * 50%.
-	if( vips_tilecache( raw, &t, 
-		"tile_width", TILE_WIDTH, 
-		"tile_height", TILE_WIDTH,
+	 */
+	if( vips_threadcache( raw, &t, 
+		"tile_width", 256, 
+		"tile_height", 256,
 		"max_tiles", (int) (1.5 * (1 + raw->Xsize / TILE_WIDTH)),
 		NULL ) ) 
 		return( -1 );
@@ -431,7 +430,6 @@ vips__openslide_read( const char *filename, VipsImage *out, int level )
 		return( -1 );
 	}
 	g_object_unref( t );
-	 */
 
 	return( 0 );
 }

libvips/include/vips/conversion.h

@@ -159,6 +159,8 @@ int vips_tilecache( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));
 int vips_linecache( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));
+int vips_threadcache( VipsImage *in, VipsImage **out, ... )
+	__attribute__((sentinel));
 int vips_sequential( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));
 int vips_cache( VipsImage *in, VipsImage **out, ... )