Issue 6465 - Maintain separate long-term cache in CombinedMatcher

lib/matcher.js

Index: lib/matcher.js
===================================================================
--- a/lib/matcher.js
+++ b/lib/matcher.js
@@ -244,24 +244,25 @@
  * @constructor
  * @augments Matcher
  */
 function CombinedMatcher()
 {
   this.blacklist = new Matcher();
   this.whitelist = new Matcher();
   this.resultCache = new Map();
+  this.frequentResultCache = new Map();
 }
 exports.CombinedMatcher = CombinedMatcher;
 
 /**
  * Maximal number of matching cache entries to be kept
  * @type {number}
  */
-CombinedMatcher.maxCacheEntries = 1000;
+CombinedMatcher.maxCacheEntries = 500;
 
 CombinedMatcher.prototype =
 {
   /**
    * Matcher for blocking rules.
    * @type {Matcher}
    */
   blacklist: null,
@@ -274,51 +275,60 @@
 
   /**
    * Lookup table of previous matchesAny results
    * @type {Map.<string,Filter>}
    */
   resultCache: null,
 
   /**
+   * Lookup table of frequently accessed previous matchesAny results
+   * @type {Map.<string,Filter>}
+   */
+  frequentResultCache: null,
+
+  /**
    * @see Matcher#clear
    */
   clear()
   {
     this.blacklist.clear();
     this.whitelist.clear();
     this.resultCache.clear();
+    this.frequentResultCache.clear();
   },
 
   /**
    * @see Matcher#add
    * @param {Filter} filter
    */
   add(filter)
   {
     if (filter instanceof WhitelistFilter)
       this.whitelist.add(filter);
     else
       this.blacklist.add(filter);
 
     this.resultCache.clear();
+    this.frequentResultCache.clear();
   },
 
   /**
    * @see Matcher#remove
    * @param {Filter} filter
    */
   remove(filter)
   {
     if (filter instanceof WhitelistFilter)
       this.whitelist.remove(filter);
     else
       this.blacklist.remove(filter);
 
     this.resultCache.clear();
+    this.frequentResultCache.clear();
   },
 
   /**
    * @see Matcher#findKeyword
    * @param {Filter} filter
    * @return {string} keyword
    */
   findKeyword(filter)
@@ -405,20 +415,31 @@
    * @see Matcher#matchesAny
    * @inheritdoc
    */
   matchesAny(location, typeMask, docDomain, thirdParty, sitekey, specificOnly)
   {
     let key = location + " " + typeMask + " " + docDomain + " " + thirdParty +
       " " + sitekey + " " + specificOnly;
 
-    let result = this.resultCache.get(key);
+    let result = this.frequentResultCache.get(key);
     if (result !== undefined)
       return result;
 
+    result = this.resultCache.get(key);
+    if (result !== undefined)
+    {
+      if (this.frequentResultCache.size >= CombinedMatcher.maxCacheEntries)
+        this.frequentResultCache.clear();
+
+      this.frequentResultCache.set(key, result);
+
+      return result;
+    }
+
     result = this.matchesAnyInternal(location, typeMask, docDomain,
                                      thirdParty, sitekey, specificOnly);
 
     if (this.resultCache.size >= CombinedMatcher.maxCacheEntries)
       this.resultCache.clear();
 
     this.resultCache.set(key, result);