UI freezes

I am finding my KNIME UI keeps freezing from a few seconds to a few minutes. This happens very often.

The behaviour is qutie  erratic in that it is not as a result of doing anything in particular. Sometimes it is when trying to open a node to set configuration, sometimes it is simply in moving a node, sometimes in just clicking on a node. The is nothing running when this happens, so it is not a processing issue.

What can I do to avoid this?

I have attached a screenshot of the workspace log , and also one of the threads expanded.



Hi David,

Weird! It's hard to diagnose the problem without having a look at the system while it's freezing. It might be helpful to look at the call stacks of the process while you experience the problem.

Can you extract a 'jstack' output and attach it here? (I described how to do it in this thread.)

Thanks (and sorry),

  - Bernd

Thanks, I'll see if I can generate a jstack output.



Hi Bernd

I retrieved this jstack log file following the instructions in the thread. This was picked up this morning, after restarting KNIME and then working until it froze again.

Please let me know if you find anything, many thanks for your help.




There is nothing in the stacktraces that indicates that the GUI is frozen. This looks like a perfectly normal situation when KNIME is waiting for work to be done. Have you tried resizing the window in such situation? Sometimes the OS won't repaint the application windows unless it's resized.

Thanks for looking through it, odd it's not showing anything.

What should I look for in the log file to indicate freezing? 

I've tried resizing, it isn't possible as the window won't respond and I just get a spinning circle.

I've retrieved the jstack from just now, when it froze. 


Hi David,

Also that stack looks perfectly normal. From the stack trace I can conclude that you are running Windows... which is even more confusing as we are not aware of any UI related problems on Windows. Usually Eclipse (the framework piece that lives underneath KNIME and makes all the OS calls) on Windows is very stable.

Few random thoughts:

  • Do you see any CPU utilization while it's frozen? (That could indicate a Java Garbage Collection cycle, which also makes the application somewhat slow to respond for a short(!) time).
  • Following up on the first point: Have you increase the knime memory size in the knime.ini file? (Default is 1G)
  • Are you using the correct archtiecture build of KNIME (64bit for 64bit OS)?
  • Which version of Windows is it?

Apologies! Clueless, so far :-(

- Bernd

Firstly, thanks for taking the time. Maybe it is the garbage collection. I'll check the CPU.

We are using 64 bit KNIME on 64 bit  machine, windows version is Windows 7 Enterprise. It may be the garbage collection, I'll keep an eye out on it. The KNIME preferences .ini file is set with -Xmx24576m, so it's 24G. The machine itself has 32G memory.

I found the UI Responsiveness Monitoring in the Preferences, and checked the Detect periods of unrepsonsive UI and Log UI freezes to Eclipse error log, and the Error Log (under View in the tool bar) does register many UI freezes. I'm not sure who to read the messages. There messages have (BLOCKED), (WAITING), (TIMED_WAITING), (RUNNABLE), etc characterising them. Which one would be responsible for a freeze?

Anyway, thanks again for taking the time.



It depends on what type of freeze it is. If it's a deadlock (which is unlikely .. not aware of any deadlock bug in KNIME) then it would be BLOCKED. Otherwise these threads are usually RUNNABLE and do something in some native call.

Freezes only occur in the 'main' and 'AWT-EventQueue-0' threads like here:

"main" #1 prio=6 os_prio=0 tid=0x00000000023ef000 nid=0x1da4 runnable [0x000000000012e000]
   java.lang.Thread.State: RUNNABLE
    at org.eclipse.swt.internal.win32.OS.WaitMessage(Native Method)
    at org.eclipse.swt.widgets.Display.sleep(Display.java:4728)
    at org.eclipse.ui.application.WorkbenchAdvisor.eventLoopIdle(WorkbenchAdvisor.java:368)

(where this is not a a freeze...)

Happy to take a look if you suspect a freeze/deadlock again.

As of this morning I’m experiencing similar 'Freezes for about 1-2 minutes at a time.
Are there any quick fixes/things to try without doing too much diagnostics?

Send the knime.log file which you’ll find in your workspace.

1 Like

Hi there,

Thanks for the quick response.

I’ve just been in touch with our IT group and it seems as though there is an issue with the network at the moment - it may be just a coincidence but I have a feeling these are related as I access the KNIME AP remotely (its installed on a server), so it’s likely that the issues are network related rather than KNIME related - I’ll wait until IT sort out the network issues and see if the KNIME issue persists before going further. Sorry for the inconvenience and the possible wrong diagnosis. Thanks Mike