don't size caches by image width

we were sizing buffers partly by image width, which could cause caches
to be too small if width changed down a pipeline

see https://github.com/jcupitt/libvips/issues/639

ChangeLog

@@ -1,3 +1,6 @@
+23/4/17 started 8.5.4
+- don't depend on image width when setting n_lines
+
 7/4/17 started 8.5.3
 - more link fixing in docs 
 - revise cache sizing again to help out of order errors under heavy load, thanks

configure.ac

@@ -2,7 +2,7 @@
 
 # also update the version number in the m4 macros below
 
-AC_INIT([vips], [8.5.3], [vipsip@jiscmail.ac.uk])
+AC_INIT([vips], [8.5.4], [vipsip@jiscmail.ac.uk])
 # required for gobject-introspection
 AC_PREREQ(2.62)
 
@@ -18,7 +18,7 @@ AC_CONFIG_MACRO_DIR([m4])
 # user-visible library versioning
 m4_define([vips_major_version], [8])
 m4_define([vips_minor_version], [5])
-m4_define([vips_micro_version], [3])
+m4_define([vips_micro_version], [4])
 m4_define([vips_version],
           [vips_major_version.vips_minor_version.vips_micro_version])
 
@@ -38,7 +38,7 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date`
 #   binary interface changes not backwards compatible?: reset age to 0
 
 LIBRARY_CURRENT=49
-LIBRARY_REVISION=3
+LIBRARY_REVISION=4
 LIBRARY_AGE=7
 
 # patched into include/vips/version.h

libvips/include/vips/threadpool.h

@@ -88,6 +88,11 @@ typedef struct _VipsThreadState {
 	 */
         void *a;
 
+	/* Set in allocate to stall this thread for a moment. Handy for
+	 * debugging race conditions.
+	 */
+	gboolean stall;
+
 } VipsThreadState;
 
 typedef struct _VipsThreadStateClass {

libvips/iofuncs/sinkdisc.c

@@ -331,6 +331,10 @@ wbuffer_allocate_fn( VipsThreadState *state, void *a, gboolean *stop )
 		sink_base->y += sink_base->tile_height;
 
 		if( sink_base->y >= VIPS_RECT_BOTTOM( &write->buf->area ) ) {
+			VIPS_DEBUG_MSG( "wbuffer_allocate_fn: "
+				"finished top = %d, height = %d\n",
+				write->buf->area.top, write->buf->area.height );
+
 			/* Block until the write of the previous buffer 
 			 * is done, then set write of this buffer going.
 			 */
@@ -346,10 +350,6 @@ wbuffer_allocate_fn( VipsThreadState *state, void *a, gboolean *stop )
 				return( 0 );
 			}
 
-			VIPS_DEBUG_MSG( "wbuffer_allocate_fn: "
-				"finished top = %d, height = %d\n",
-				write->buf->area.top, write->buf->area.height );
-
 			VIPS_DEBUG_MSG( "wbuffer_allocate_fn: "
 				"starting top = %d, height = %d\n",
 				sink_base->y, sink_base->nlines );
@@ -365,6 +365,11 @@ wbuffer_allocate_fn( VipsThreadState *state, void *a, gboolean *stop )
 				*stop = TRUE;
 				return( -1 );
 			}
+
+			/* This will be the first tile of a new buffer ...
+			 * stall for a moment to stress the caching system.
+			 */
+			state->stall = TRUE;
 		}
 	}
 

libvips/iofuncs/threadpool.c

@@ -18,6 +18,9 @@
  * 6/3/17
  * 	- remove single-thread-first-request thing, new seq system makes it
  * 	  unnecessary
+ * 23/4/17
+ * 	- add ->stall
+ * 	- don't depend on image width when setting n_lines
  */
 
 /*
@@ -111,6 +114,10 @@ int vips__n_active_threads = 0;
  */
 static GPrivate *is_worker_key = NULL;
 
+/* Set to stall threads for debugging.
+ */
+static gboolean vips__stall = FALSE;
+
 /* Glib 2.32 revised the thread API. We need some compat functions.
  */
 
@@ -466,6 +473,7 @@ vips_thread_state_init( VipsThreadState *state )
 
 	state->reg = NULL;
 	state->stop = FALSE;
+	state->stall = FALSE;
 }
 
 void *
@@ -634,6 +642,17 @@ vips_thread_work_unit( VipsThread *thr )
 
 	g_mutex_unlock( pool->allocate_lock );
 
+	if( thr->state->stall &&
+		vips__stall ) { 
+		/* Sleep for 0.5s. Handy for stressing the seq system. Stall
+		 * is set by allocate funcs in various places. 
+		 */
+		g_usleep( 500000 ); 
+		thr->state->stall = FALSE;
+		printf( "vips_thread_work_unit: "
+			"stall done, releasing y = %d ...\n", thr->state->y ); 
+	}
+
 	/* Process a work unit.
 	 */
 	if( pool->work( thr->state, pool->a ) ) { 
@@ -999,6 +1018,9 @@ vips__threadpool_init( void )
 	if( !is_worker_key ) 
 		is_worker_key = g_private_new( NULL ); 
 #endif
+
+	if( g_getenv( "VIPS_STALL" ) )
+		vips__stall = TRUE;
 }
 
 /**
@@ -1021,6 +1043,7 @@ vips_get_tile_size( VipsImage *im,
 	int *tile_width, int *tile_height, int *n_lines )
 {
 	const int nthr = vips_concurrency_get();
+	const int typical_image_width = 1000;
 
 	/* Compiler warnings.
 	 */
@@ -1054,11 +1077,15 @@ vips_get_tile_size( VipsImage *im,
 	 * the pipeline might see a different hint and we need to synchronise
 	 * buffer sizes everywhere.
 	 *
+	 * We also can't depend on the current image size, since that might
+	 * change down the pipeline too. Pick a typical image width.
+	 *
 	 * Pick the maximum buffer size we might possibly need, then round up
 	 * to a multiple of tileheight.
 	 */
 	*n_lines = vips__tile_height * 
-		VIPS_ROUND_UP( vips__tile_width * nthr, im->Xsize ) / im->Xsize;
+		VIPS_ROUND_UP( vips__tile_width * nthr, typical_image_width ) / 
+			typical_image_width;
 	*n_lines = VIPS_MAX( *n_lines, vips__fatstrip_height * nthr );
 	*n_lines = VIPS_MAX( *n_lines, vips__thinstrip_height * nthr );
 	*n_lines = VIPS_ROUND_UP( *n_lines, *tile_height );