diff --git a/djvu.c b/djvu.c
index a5ab8380f..a97a4f610 100644
--- a/djvu.c
+++ b/djvu.c
@@ -71,7 +71,6 @@ static int handle(lua_State *L, ddjvu_context_t *ctx, int wait)
 
 static int openDocument(lua_State *L) {
 	const char *filename = luaL_checkstring(L, 1);
-	/*const char *password = luaL_checkstring(L, 2);*/
 	int cache_size = luaL_optint(L, 2, 10 << 20);
 
 	DjvuDocument *doc = (DjvuDocument*) lua_newuserdata(L, sizeof(DjvuDocument));
@@ -82,6 +81,8 @@ static int openDocument(lua_State *L) {
 	if (! doc->context) {
 		return luaL_error(L, "cannot create context.");
 	}
+
+	printf("## cache_size = %d\n", cache_size);
 	ddjvu_cache_set_size(doc->context, (unsigned long)cache_size);
 
 	doc->doc_ref = ddjvu_document_create_by_filename_utf8(doc->context, filename, TRUE);
@@ -449,6 +450,21 @@ static int drawPage(lua_State *L) {
 	return 0;
 }
 
+static int getCacheSize(lua_State *L) {
+	DjvuDocument *doc = (DjvuDocument*) luaL_checkudata(L, 1, "djvudocument");
+	unsigned long size = ddjvu_cache_get_size(doc->context);
+	printf("## ddjvu_cache_get_size = %d\n", size);
+	lua_pushnumber(L, size);
+	return 1;
+}
+
+static int cleanCache(lua_State *L) {
+	DjvuDocument *doc = (DjvuDocument*) luaL_checkudata(L, 1, "djvudocument");
+	printf("## ddjvu_cache_clear\n");
+	ddjvu_cache_clear(doc->context);
+	return 0;
+}
+
 static const struct luaL_Reg djvu_func[] = {
 	{"openDocument", openDocument},
 	{NULL, NULL}
@@ -460,6 +476,8 @@ static const struct luaL_Reg djvudocument_meth[] = {
 	{"getTOC", getTableOfContent},
 	{"getPageText", getPageText},
 	{"close", closeDocument},
+	{"getCacheSize", getCacheSize},
+	{"cleanCache", cleanCache},
 	{"__gc", closeDocument},
 	{NULL, NULL}
 };
diff --git a/djvureader.lua b/djvureader.lua
index 0d38faf55..be72ec4c0 100644
--- a/djvureader.lua
+++ b/djvureader.lua
@@ -6,7 +6,7 @@ DJVUReader = UniReader:new{}
 -- DJVU does not support password yet
 function DJVUReader:open(filename)
 	local ok
-	ok, self.doc = pcall(djvu.openDocument, filename, 10*1024*1024)
+	ok, self.doc = pcall(djvu.openDocument, filename, self.cache_document_size)
 	if not ok then
 		return ok, self.doc -- this will be the error message instead
 	end
diff --git a/pdf.c b/pdf.c
index 5583e09a0..ffa94be2e 100644
--- a/pdf.c
+++ b/pdf.c
@@ -164,16 +164,16 @@ fz_alloc_context my_alloc_default =
 
 static int openDocument(lua_State *L) {
 	char *filename = strdup(luaL_checkstring(L, 1));
-	int cachesize = luaL_optint(L, 2, 64 << 20); // 64 MB limit default
+	int cache_size = luaL_optint(L, 2, 64 << 20); // 64 MB limit default
 	char buf[15];
-	printf("cachesize: %s\n",readable_fs(cachesize,buf));
+	printf("## cache_size: %s\n",readable_fs(cache_size,buf));
 
 	PdfDocument *doc = (PdfDocument*) lua_newuserdata(L, sizeof(PdfDocument));
 
 	luaL_getmetatable(L, "pdfdocument");
 	lua_setmetatable(L, -2);
 
-	doc->context = fz_new_context(&my_alloc_default, NULL, cachesize);
+	doc->context = fz_new_context(&my_alloc_default, NULL, cache_size);
 
 	fz_try(doc->context) {
 		doc->xref = fz_open_document(doc->context, filename);
diff --git a/pdfreader.lua b/pdfreader.lua
index ec4e1a105..9413e0127 100644
--- a/pdfreader.lua
+++ b/pdfreader.lua
@@ -8,7 +8,7 @@ function PDFReader:open(filename)
 	-- muPDF manages its own cache, set second parameter
 	-- to the maximum size you want it to grow
 	local ok
-	ok, self.doc = pcall(pdf.openDocument, filename, 64*1024*1024)
+	ok, self.doc = pcall(pdf.openDocument, filename, self.cache_document_size)
 	if not ok then
 		return false, self.doc -- will contain error message
 	end
diff --git a/unireader.lua b/unireader.lua
index b2cb982a1..939e6848a 100644
--- a/unireader.lua
+++ b/unireader.lua
@@ -72,6 +72,8 @@ UniReader = {
 	-- tile cache state:
 	cache_current_memsize = 0,
 	cache = {},
+	-- renderer cache size
+	cache_document_size = 1024*1024*8, -- FIXME random, needs testing
 
 	pagehash = nil,
 
@@ -105,7 +107,7 @@ end
 
 -- open a file and its settings store
 -- tips: you can use self:loadSettings in open() method.
-function UniReader:open(filename, password)
+function UniReader:open(filename, cache_size)
 	return false
 end
 
@@ -126,12 +128,24 @@ function UniReader:toggleTextHighLight(word_list)
 	return
 end
 
+----------------------------------------------------
+-- renderer memory
+----------------------------------------------------
+
+function UniReader:getCacheSize()
+	return -1
+end
+
+function UniReader:cleanCache()
+	return
+end
+
 
 --[ following are default methods ]--
 
 function UniReader:loadSettings(filename)
 	if self.doc ~= nil then
-		self.settings = DocSettings:open(filename)
+		self.settings = DocSettings:open(filename,self.cache_document_size)
 
 		local gamma = self.settings:readSetting("gamma")
 		if gamma then
@@ -804,6 +818,15 @@ function UniReader:showMenu()
 	ypos = ypos + 15
 	blitbuffer.progressBar(fb.bb, 10, ypos, width-20, 15,
 							5, 4, load_percent, 8)
+
+	-- display memory on top of page
+	fb.bb:paintRect(0, 0, width, 15+6*2, 0)
+	renderUtf8Text(fb.bb, 10, 15+6, face, fhash,
+		"Memory: "..
+		math.ceil( self.cache_current_memsize / 1024 ).."/"..( self.cache_max_memsize / 1024 )..
+		" "..( self.cache_item_max_pixels / 1024 ).." "..( self.cache_document_size / 1024 ).." k",
+	true)
+
 	fb:refresh(1)
 	while 1 do
 		local ev = input.waitForEvent()
@@ -811,6 +834,8 @@ function UniReader:showMenu()
 		if ev.type == EV_KEY and ev.value == EVENT_VALUE_KEY_PRESS then
 			if ev.code == KEY_BACK or ev.code == KEY_MENU then
 				return
+			elseif ev.code == KEY_C then
+				self.doc:cleanCache()
 			end
 		end
 	end