sun.awt.X11.XEvent is creating 600 MB of char[] for no good reason (original) (raw)

Federico Tello Gentile federicotg at gmail.com
Thu Oct 20 20:10:11 PDT 2011

Hi. I'm running

java -version java version "1.7.0_147-icedtea" OpenJDK Runtime Environment (IcedTea7 2.0pre) (7b147-2.0pre6-1ubuntu1) OpenJDK 64-Bit Server VM (build 21.0-b17, mixed mode)

and profiling a simple Swing application.

Just by opening a JFrame and moving the mouse over it for 10 secods I see 600 MB of char[] being created. I can easily create several terabytes or those if I move the mouse a little longer. Thanks to the incredibly efficient garbage collector the application performance is not visibly affected on my 4GB quad core machine.

The problem is an incredibly inefficient method

sun.awt.X11.XEvent.getFieldsAsString() which I pasted at the end of this message.

The way it it handling string concatenation forces StringBuilder to grow many times and ends up calling Arrays.copyOf a lot of times.

It is being called by the sun.awt.X11.XWrapperBase.toString() just for the sake of logging here:

sun.awt.X11.XComponentPeer

protected boolean isEventDisabled(XEvent e)

enableLog.finest("Component is {1}, checking for disabled event {0}", e, (isEnabled()?"enabled":"disable"));

The worse part is that even if logging is disabled and nothing at all is ever logged, the toString is called anyway and all those char[] are created anyway.

Here's a NetBeans profiler memory snapshot.

http://ubuntuone.com/4xkprEzadUM4sUSdAnWlN5

This does not happen at all if I run the same profiling with this openjdk version

java -version java version "1.6.0_23" OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre10-0ubuntu5) OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)

I hope we can do something to improve this situation. I guess all Swing applications are affected.

I look forward for any comments.

Here's the "thing"...

String getFieldsAsString() { String ret="";

    ret += ""+"type = " + XlibWrapper.eventToString[get_type()] +", ";
    ret += ""+"xany = " + get_xany() +", ";
    ret += ""+"xkey = " + get_xkey() +", ";
    ret += ""+"xbutton = " + get_xbutton() +", ";
    ret += ""+"xmotion = " + get_xmotion() +", ";
    ret += ""+"xcrossing = " + get_xcrossing() +", ";
    ret += ""+"xfocus = " + get_xfocus() +", ";
    ret += ""+"xexpose = " + get_xexpose() +", ";
    ret += ""+"xgraphicsexpose = " + get_xgraphicsexpose() +", ";
    ret += ""+"xnoexpose = " + get_xnoexpose() +", ";
    ret += ""+"xvisibility = " + get_xvisibility() +", ";
    ret += ""+"xcreatewindow = " + get_xcreatewindow() +", ";
    ret += ""+"xdestroywindow = " + get_xdestroywindow() +", ";
    ret += ""+"xunmap = " + get_xunmap() +", ";
    ret += ""+"xmap = " + get_xmap() +", ";
    ret += ""+"xmaprequest = " + get_xmaprequest() +", ";
    ret += ""+"xreparent = " + get_xreparent() +", ";
    ret += ""+"xconfigure = " + get_xconfigure() +", ";
    ret += ""+"xgravity = " + get_xgravity() +", ";
    ret += ""+"xresizerequest = " + get_xresizerequest() +", ";
    ret += ""+"xconfigurerequest = " + get_xconfigurerequest() +", ";
    ret += ""+"xcirculate = " + get_xcirculate() +", ";
    ret += ""+"xcirculaterequest = " + get_xcirculaterequest() +", ";
    ret += ""+"xproperty = " + get_xproperty() +", ";
    ret += ""+"xselectionclear = " + get_xselectionclear() +", ";
    ret += ""+"xselectionrequest = " + get_xselectionrequest() +", ";
    ret += ""+"xselection = " + get_xselection() +", ";
    ret += ""+"xcolormap = " + get_xcolormap() +", ";
    ret += ""+"xclient = " + get_xclient() +", ";
    ret += ""+"xmapping = " + get_xmapping() +", ";
    ret += ""+"xerror = " + get_xerror() +", ";
    ret += ""+"xkeymap = " + get_xkeymap() +", ";
    ret += "{" + get_pad(0) + " " + get_pad(1) + " " + get_pad(2) + " " +

get_pad(3) + " " + get_pad(4) + " " + get_pad(5) + " " + get_pad(6) + " " + get_pad(7) + " " + get_pad(8) + " " + get_pad(9) + " " + get_pad(10)

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