Comment 0 for bug 277069

Created an attachment (id=19336)
tshark-dump of one keypress with XCB linked in

Some Java applications, such as the trial version in http://www.typingmaster.com/, run unusably slow when used over a remote X connection.

I'm using Ubuntu Hardy 8.04.1 with LTSP5, Linux kernel 2.6.24-19-server, with 32-bit firefox and 32-bit Java-plugin. The relevant package versions are here:

firefox32 2.0.0.17
sun-java32 1.6.0.5
sun-java6-jre 6-06-0ubuntu1
ia32-libs 2.2ubuntu11
libxcb1 1.1-1ubuntu1
libxcb-xlib0 1.1-1ubuntu1

The issue does not appear to be Java-version related (it exists in 1.5 and 1.6 versions). I have not tested the very latest Java-versions though. The reason I'm reporting this as a possible XCB-related issue is that one can workaround the problem by using an X11-library that does not link to XCB.

In current Ubuntu version (Hardy), /usr/lib32/libX11.so.6.2.0 library links to /usr/lib32/libxcb-xlib.so.0 and /usr/lib32/libxcb.so.1 libraries, XCB version is 1.1. In previous Ubuntu version (Gutsy) the X11-library does not do this. When the new library shared object replaced with the old one, the problem disappears, and Java applications that had problems run fine.

There may be some other differences between the X11-libraries, but using XCB as an underlying implementation seems to be a major change, or is it? All other applications do not appear to have these problems, Java applications appear to be the sole source of these problems.

I'm adding two attachments that show tshark-dump of network traffic in both cases, perhaps it helps to analyze the issue. What happens there is one keypress on typingmaster Java-version, on Hardy/XCB case it takes half a minute to process one keypress and switch a screen, on Gutsy/no-XCB case it takes maybe a second.

Juha