Issue #3030 - Improve image cache entry handling.

This:
- increases max image cache entry size and adjusts related parameters.
- makes the cache entry timeout configurable for advanced tweaking.
- adds a mechanism to keep commonly-used, small image sizes in cache
  longer.

gfx/thebes/gfxPrefs.h

@@ -436,6 +436,7 @@ private:
   DECL_GFX_PREF(Live, "image.animated.resume-from-last-displayed", ImageAnimatedResumeFromLastDisplayed, bool, false);
   DECL_GFX_PREF(Once, "image.cache.size",                      ImageCacheSize, int32_t, 5*1024*1024);
   DECL_GFX_PREF(Once, "image.cache.timeweight",                ImageCacheTimeWeight, int32_t, 500);
+  DECL_GFX_PREF(Once, "image.cache.entry_timeout",             ImageCacheEntryTimeout, int32_t, 15000);
   DECL_GFX_PREF(Live, "image.decode-immediately.enabled",      ImageDecodeImmediatelyEnabled, bool, false);
   DECL_GFX_PREF(Live, "image.downscale-during-decode.enabled", ImageDownscaleDuringDecodeEnabled, bool, true);
   DECL_GFX_PREF(Live, "image.infer-src-animation.threshold-ms", ImageInferSrcAnimationThresholdMS, uint32_t, 2000);

image/VectorImage.cpp

@@ -936,9 +936,9 @@ VectorImage::CreateSurfaceAndShow(const SVGDrawingParameters& aParams, BackendTy
   // are scaled repeatedly (a rather common scenario) that can quickly exhaust
   // the cache.
   // Similar to max image size calculations, this has a max cap and size check.
-  // max cap = 8000 (pixels); size check = 5% of cache
+  // max cap = 8000 (pixels); size check = 10% of cache
   int32_t maxDimension = 8000;
-  int32_t maxCacheElemSize = (gfxPrefs::ImageMemSurfaceCacheMaxSizeKB() * 1024) / 20;
+  int32_t maxCacheElemSize = (gfxPrefs::ImageMemSurfaceCacheMaxSizeKB() * 1024) / 10;
   
   bool bypassCache = bool(aParams.flags & FLAG_BYPASS_SURFACE_CACHE) ||
                      // Refuse to cache animated images:

image/imgLoader.cpp

@@ -1087,7 +1087,6 @@ imgLoader::CreateNewProxyForRequest(imgRequest* aRequest,
 class imgCacheExpirationTracker final
   : public nsExpirationTracker<imgCacheEntry, 3>
 {
-  enum { TIMEOUT_SECONDS = 10 };
 public:
   imgCacheExpirationTracker();
 
@@ -1096,10 +1095,46 @@ protected:
 };
 
 imgCacheExpirationTracker::imgCacheExpirationTracker()
- : nsExpirationTracker<imgCacheEntry, 3>(TIMEOUT_SECONDS * 1000,
+ : nsExpirationTracker<imgCacheEntry, 3>(gfxPrefs::ImageCacheEntryTimeout(),
                                          "imgCacheExpirationTracker")
 { }
 
+static bool
+ShouldKeepRecentlyUsedAssetInCache(imgCacheEntry* aEntry)
+{
+  RefPtr<imgRequest> request = aEntry->GetRequest();
+  if (!request) {
+    return false;
+  }
+
+  const char* mimeType = request->GetMimeType();
+  if (!mimeType) {
+    return false;
+  }
+
+  // Keep small, frequently reused static image assets warm a bit longer.
+  if (!nsCRT::strcmp(mimeType, IMAGE_SVG_XML) ||
+      !nsCRT::strcmp(mimeType, IMAGE_JPG) ||
+      !nsCRT::strcmp(mimeType, IMAGE_JPEG) ||
+      !nsCRT::strcmp(mimeType, IMAGE_ICO) ||
+      !nsCRT::strcmp(mimeType, IMAGE_PNG) ||
+      !nsCRT::strcmp(mimeType, IMAGE_WEBP)) {
+    // XXX: Should we make these configurable too?
+    const uint32_t kMaxWarmAssetBytes = 128 * 1024; // <= 128 kiB entries only
+    const uint32_t kRecentUseGraceSeconds = 60;     // keep warm for 60 s
+
+    if (aEntry->GetDataSize() <= kMaxWarmAssetBytes) {
+      uint32_t now = SecondsFromPRTime(PR_Now());
+      uint32_t touched = aEntry->GetTouchedTime();
+      if (now >= touched && (now - touched) <= kRecentUseGraceSeconds) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
 void
 imgCacheExpirationTracker::NotifyExpired(imgCacheEntry* entry)
 {
@@ -1107,6 +1142,12 @@ imgCacheExpirationTracker::NotifyExpired(imgCacheEntry* entry)
   // mechanism doesn't.
   RefPtr<imgCacheEntry> kungFuDeathGrip(entry);
 
+  if (ShouldKeepRecentlyUsedAssetInCache(entry)) {
+    entry->Touch();
+    entry->Loader()->VerifyCacheSizes();
+    return;
+  }
+
   if (MOZ_LOG_TEST(gImgLog, LogLevel::Debug)) {
     RefPtr<imgRequest> req = entry->GetRequest();
     if (req) {

image/imgLoader.h

@@ -152,6 +152,7 @@ public:
 private: // methods
   friend class imgLoader;
   friend class imgCacheQueue;
+  friend class imgCacheExpirationTracker;
   void Touch(bool updateTime = true);
   void UpdateCache(int32_t diff = 0);
   void SetEvicted(bool evict)

modules/libpref/init/all.js

@@ -4262,12 +4262,18 @@ pref("image.animated.decode-on-demand.batch-size", 6);
 // advancing when out of view.
 pref("image.animated.resume-from-last-displayed", true);
 
+// Image cache prefs: Restart required for changes.
+
 // The maximum size, in bytes, of the decoded images we cache
-pref("image.cache.size", 5242880);
+pref("image.cache.size", 26214400);
 
 // A weight, from 0-1000, to place on time when comparing to size.
 // Size is given a weight of 1000 - timeweight.
-pref("image.cache.timeweight", 500);
+pref("image.cache.timeweight", 650);
+
+// Time in ms before unproxied entries in the in-memory image cache are
+// considered for eviction by the expiration tracker.
+pref("image.cache.entry_timeout", 15000);
 
 // Decode all images automatically on load, ignoring our normal heuristics.
 pref("image.decode-immediately.enabled", false);
@@ -4314,7 +4320,7 @@ pref("image.mem.decode_bytes_at_a_time", 16384);
 
 // Minimum timeout for expiring unused images from the surface cache, in
 // milliseconds. This controls how long we store cached temporary surfaces.
-pref("image.mem.surfacecache.min_expiration_ms", 60000); // 60s
+pref("image.mem.surfacecache.min_expiration_ms", 180000); // 180s
 
 // Maximum size for the surface cache, in kilobytes.
 pref("image.mem.surfacecache.max_size_kb", 1048576); // 1GB
@@ -4331,7 +4337,7 @@ pref("image.mem.surfacecache.size_factor", 4);
 // surface cache on memory pressure, a discard factor of 2 means to discard half
 // of the data, and so forth. The default should be a good balance for desktop
 // and laptop systems, where we never discard visible images.
-pref("image.mem.surfacecache.discard_factor", 1);
+pref("image.mem.surfacecache.discard_factor", 2);
 
 // How many threads we'll use for multithreaded decoding. If < 0, will be
 // automatically determined based on the system's number of cores.