SCI: Increase LRU resource cache for SCI32 games

A single picture in SCI32 is often larger than the 256KiB limit,
meaning that the cache is useless for these games -- which is bad,
because the renderer works directly off raw resource data so it
must be decompressed and in-cache for rendering performance to be
acceptable.

2 files changed, 11 insertions, 4 deletions

diff --git a/engines/sci/resource.cpp b/engines/sci/resource.cpp
index 92d35ba1fc..86c5f52455 100644
--- a/engines/sci/resource.cpp
+++ b/engines/sci/resource.cpp
@@ -865,6 +865,7 @@ ResourceManager::ResourceManager() {
 }
 
 void ResourceManager::init() {
+	_maxMemoryLRU = 256 * 1024; // 256KiB
 	_memoryLocked = 0;
 	_memoryLRU = 0;
 	_LRU.clear();
@@ -918,6 +919,14 @@ void ResourceManager::init() {
 
 	debugC(1, kDebugLevelResMan, "resMan: Detected %s", getSciVersionDesc(getSciVersion()));
 
+	// Resources in SCI32 games are significantly larger than SCI16
+	// games and can cause immediate exhaustion of the LRU resource
+	// cache, leading to constant decompression of picture resources
+	// and making the renderer very slow.
+	if (getSciVersion() >= SCI_VERSION_2) {
+		_maxMemoryLRU = 2048 * 1024; // 2MiB
+	}
+
 	switch (_viewType) {
 	case kViewEga:
 		debugC(1, kDebugLevelResMan, "resMan: Detected EGA graphic resources");
@@ -1023,7 +1032,7 @@ void ResourceManager::printLRU() {
 }
 
 void ResourceManager::freeOldResources() {
-	while (MAX_MEMORY < _memoryLRU) {
+	while (_maxMemoryLRU < _memoryLRU) {
 		assert(!_LRU.empty());
 		Resource *goner = *_LRU.reverse_begin();
 		removeFromLRU(goner);
diff --git a/engines/sci/resource.h b/engines/sci/resource.h
index eb5b508254..46ac2bb944 100644
--- a/engines/sci/resource.h
+++ b/engines/sci/resource.h
@@ -426,9 +426,7 @@ protected:
 	// Note: maxMemory will not be interpreted as a hard limit, only as a restriction
 	// for resources which are not explicitly locked. However, a warning will be
 	// issued whenever this limit is exceeded.
-	enum {
-		MAX_MEMORY = 256 * 1024	// 256KB
-	};
+	int _maxMemoryLRU;
 
 	ViewType _viewType; // Used to determine if the game has EGA or VGA graphics
 	Common::List<ResourceSource *> _sources;