Tree "Expand All" taking too much time for a large tree

Hi All,
I am facing  a problem with dojo tree.
The requirement is to display a dojo tree as default expanded and also user can click on "Expand All" which will alow the tree to expand.
For both these activities I am using a  java script function:

 function expandAllNode()
 {
 var treeObj = dijit.byId('mytree');
       
 var children = treeObj.rootNode.getChildren();
 expandChildNode(children, treeObj);

 }

 function expandChildNode(children, treeObj)
 {
 for (var i = 0; i < children.length; i++)
 {
 var node = children[i];
 if (node.isExpandable && !node.isExpanded)
 {
 treeObj._expandNode(node);
 }

 var childNodes = node.getChildren();
 if (childNodes.length > 0)
 {
 expandChildNode(childNodes, treeObj);
 }
 }
 }        
Now for auto expand I am calling it by  
dojo.addOnLoad(function(){
               
                timer = setTimeout("expandAllNode()",1000);
                highlightNode();
                               
        });

Problem:  The problem is If the tree is too large it will not being  expanded by default within 1000 millisecond.
Also if the  tree is too small first it showing in collapse mode the its expanding after a bit of second.
Also for a big tree Expand All is taking too much time (some times may be more 1 min have to wait for Expand All)

Can you please help me by providing a robus sollution which will  allow me to auto expand as well as Expand All.

regards
Pronab

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