[vbox-dev] API method execution sometimes extremely slow

Klaus Espenlaub klaus.espenlaub at oracle.com
Wed Dec 11 12:14:04 GMT 2013

Hi Thorsten,

On 10.12.2013 14:44, email at thorstenschaefer.de wrote:
> Hi,
> I am using VirtualBox 4.3.4 on MacOS Maverick. The VM is a Windows 7
> 64bit guest running on a Macbook Pro (8 cores, 16GB RAM). The issue I
> have is as described at
> https://forums.virtualbox.org/viewtopic.php?f=34&t=57685:
> When using the API methods over Java using XPCOM, some method calls
> randomly take a huge amount of time. For instance, things that are
> typically done within 1-5ms sometimes take up to 2000ms! Even when these
> delays happen, the CPU usage is never even near 100% and their is
> sufficient free memory on the host available. I wonder if someone can
> give me insights into what might cause these kind of delays and if its
> maybe possible to communicate more quickly. For instance, if its caused
> by interprocess scheduling, is it possible to “open a stream” and then
> just send the commands to it? Fwiw, if I perform the same stuff (e.g.
> Key clicks) manually within the VM, there are never delays like this
> observable.

Never seen such problems, and as the Java/XPCOM combo in the end 
interfaces to the C++ API which is used by every VirtualBox component 
(the manager GUI and the VM processes) I doubt that there's a generic issue.

When does the big delay happen? Is it really for individual API calls, 
or do you count in the setup time (getting the VirtualBox reference, 
setting up a session)?

We don't write much Java code, and don't actively use this way of 
talking to the API, but we're quite sure that more than only a few 
people go this way.


> Cheers,
> Thorsten

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