Re: GNOME performance [Was: the same page]

[Alan Cox <alan redhat com>]

> So, whilst this is something we ought to put at the back of our minds with a
> major release coming up, some simple guides to stracing/profiling GNOME
> applications and pinpointing performance problems may come in handy. Anyone
> have pointers or documentation already available for contributors to look
> at?

Some suggestions

Use strace on gnome applications and you can measure how long it is before
things like library loading occur. Some of those are far longer than anyone
would like. That tells you the startup costs

On non threaded apps ltrace can give you time per call data for library
usage by an application. Bonobo when I looked at nautilus was not pretty
but I know Michael has done stuff there since. 

gprof will tell you where your application is spending CPU time (but with
100Hz accuracy so it can be misleading at times) and also show you the
function call graphs and the average times per call. Its a wonderful tool
although it lacks good visualisation tools to go with it (but then Gnome
has nice visualisation tools so spot the project)

For start up time my first suggestion having looked at the I/O patterns
at kernel level even with the prelinking stuff is that someone should 
dig out Nat Friedman's old grope project and profile an app up to the point
its "active" then relink the apps and libraries start up code paths in an order
based on the order that pages are accessed. That will cut down on a lot of
seeking as the binary is paged in the first time.

[Typical IDE disk throughput nowdays is 30-40Mbytes/second linear, 1-2Mbytes
 a second seeking hard]

Alan
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