<AWT Dev> sun.awt.X11.XEvent is creating 600 MB of char[] for no good reason

[Anthony Petrov]

On 10/26/2011 7:12 PM, Artem Ananiev wrote:
> On 10/21/2011 4:00 PM, Anthony Petrov wrote:
>> Indeed, this is a nasty issue. Thanks for spotting it. You may notice
>> that in most other places where something is logged, the code usually
>> checks whether logging is enabled for a certain level of logging, e.g.:
>>
>>> if (shapeLog.isLoggable(PlatformLogger.FINER)) {
>>> shapeLog.finer(
>>> "*** INFO: Setting shape: PEER: " + this
>>> + "; WINDOW: " + getWindow()
>>> + "; TARGET: " + target
>>> + "; SHAPE: " + shape);
>>> }
>>
>> So basically, we could simply wrap the line in question into a similar
>> if(){} statement to make sure it gets executed only when the FINEST
>> level of logging is enabled. A similar solution may also apply to
>> another call to enableLog.finer() in the same method just a few lines
>> below.
> 
> Although the fix has been already pushed to the workspace, let me wonder 
> if, in addition to wrapping the logging calls with the "if ()" checks, 
> we should have also rewritten isEventDisabled() to use StringBuilder?

I guess you really mean the XEvent.getFieldsAsString() here [1], right? 
Possibly. But with Federico's fix this method now only gets called when 
logging is enabled, and as such the impact of the issue is limited.

[1] http://mail.openjdk.java.net/pipermail/awt-dev/2011-October/001952.html

--
best regards,
Anthony


> 
> Thanks,
> 
> Artem
> 
>> Could you make a patch, test it, and post it to this mailing list for
>> review please?
>>
>> -- 
>> best regards,
>> Anthony
>>
>> On 10/21/2011 7:10 AM, Federico Tello Gentile wrote:
>>> Hi.
>>> I'm running
>>>
>>> java -version
>>> java version "1.7.0_147-icedtea"
>>> OpenJDK Runtime Environment (IcedTea7 2.0pre) (7~b147-2.0~pre6-1ubuntu1)
>>> 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)
>>> + " " + get_pad(11) + " " + get_pad(12) + " " + get_pad(13) + " " +
>>> get_pad(14) + " " + get_pad(15) + " " + get_pad(16) + " " + get_pad(17)
>>> + " " + get_pad(18) + " " + get_pad(19) + " " + get_pad(20) + " " +
>>> get_pad(21) + " " + get_pad(22) + " " + get_pad(23) + " " + "}";
>>> return ret;
>>> }
>>>
>>>