Performance techniques and tools.

[Jim Gettys <jg freedesktop org>]

Performance tools:

X is a client/server system.  It is (relatively) simple to set up a set
of machines that separate the client and the X server, and then look at
the network traffic between them.  It is *very* enlightening to look at
these traces.

Keith Packard and I did this for our performance work some years ago.
See: http://keithp.com/~keithp/talks/usenix2003/ for a description of
this.  It is really worth downloading the tool for graphing the packet
traces vs. time and look at what is going on; we traced a full gnome
session startup.

The code for the tools is available.

A *wonderful* addition would be to add system call traces to the plots,
and/or other kernel system traces.  See http://www.opersys.com/LTT/ for
one of the systems that is available for Linux.  There is also very good
tracing tools (non-invasive) available on Solaris.  Some scripts to take
such traces and combine them with the X traffic traces would allow one
to see what is going on when applications aren't doing anything with X.

These might then identify what is going on in the long periods of time
that Gnome is doing nothing before things get started, though Nat may
have identified Gnome-session as being particularly brain-dead.
                              - Jim