timers: optimize linkedlist

Now uses a new L.create() factory to create access-optimized linkedlist
objects.
PR-URL: #6436
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: Andras

lib/internal/linkedlist.js

@@ -6,6 +6,13 @@ function init(list) {
 }
 exports.init=init;
 
+// create a new linked list
+functioncreate(){
+varlist={_idleNext: null,_idlePrev: null};
+init(list);
+returnlist;
+}
+exports.create=create;
 
 // show the most idle item
 functionpeek(list){
@@ -42,10 +49,17 @@ exports.remove = remove;
 
 // remove a item from its list and place at the end.
 functionappend(list,item){
-remove(item);
+if(item._idleNext||item._idlePrev){
+remove(item);
+}
+
+// items are linked with _idleNext -> (older) and _idlePrev -> (newer)
+// TODO: swap the linkage to match the intuitive older items at "prev"
 item._idleNext=list._idleNext;
-list._idleNext._idlePrev=item;
 item._idlePrev=list;
+
+// the list _idleNext points to tail (newest) and _idlePrev to head (oldest)
+list._idleNext._idlePrev=item;
 list._idleNext=item;
 }
 exports.append=append;

lib/timers.js

@@ -502,16 +502,14 @@ Timeout.prototype.close = function() {
 };
 
 
-varimmediateQueue={};
-L.init(immediateQueue);
+varimmediateQueue=L.create();
 
 
 functionprocessImmediate(){
 varqueue=immediateQueue;
 vardomain,immediate;
 
-immediateQueue={};
-L.init(immediateQueue);
+immediateQueue=L.create();
 
 while(L.isEmpty(queue)===false){
 immediate=L.shift(queue);

test/parallel/test-timers-linked-list.js

@@ -103,3 +103,8 @@ assert.equal(C, L.shift(list));
 // list
 assert.ok(L.isEmpty(list));
 
+varlist2=L.create();
+varlist3=L.create();
+assert.ok(L.isEmpty(list2));
+assert.ok(L.isEmpty(list3));
+assert.ok(list2!=list3);