[TACHYON-220] WIP Comments describing issues and possible solutions 

Some initial comments to help improve the performance of master info. From what I gather there is locking on stack local objects that are never really put back into the map. I would appreciate suggestions before implementing it, hence the WIP tag.
Thanks. I'll look to send a patch to remove that.
On Nov 20, 2014 9:52 AM, "Manu Goyal" <notifications@github.com> wrote:

> In core/src/main/java/tachyon/master/MasterInfo.java:
>
> > @@ -1527,6 +1525,24 @@ public TachyonURI getPath(int fileId) throws FileDoesNotExistException {
> >    }
> >
> >    /**
> > +   * Get the path specified by a given inode. Should only be called
> > +   * within a synchronized call e.g. {@link MasterInfo#getPath(tachyon.master.Inode)}.
> > +   * This is because calling sync repeatedly within a recursive method results in
> > +   * poor performance. So this method must be called in a synchronized way.
> > +   * @param inode The inode
> > +   * @return the path of the inode
> > +   */
> > +  private TachyonURI getPathUsingRecursion(Inode inode) {
>
> Yeah, pretty much all the MasterInfo methods have a helper method that
> starts with an underscore, like _addCheckpoint, _createFile, _delete, _ls,
> etc.
>
> —
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> <https://github.com/amplab/tachyon/pull/527/files#r20664005>.
>