Re: Login time

[Rob Taylor <rob taylor codethink co uk>]

Federico Mena Quintero wrote:
> El mar, 10-04-2007 a las 10:54 -0400, Michael R. Head escribi� 
>> Doesn't strace drastically affect performance? I thought the goal was to
>> see how long these parts of the login process take under normal
>> conditions.
> 
> #include <uncertainty-principle.h>
> 
> The overhead from strace doesn't seem to be terrible... it's certainly
> better than not being able to get any timings at all :)  I haven't timed
> it with a stopwatch, though.
> 
> I'd *love* to use a less pedestrian tool.  Does anyone know if Systemtap
> is mature enough for this?  We'd need to say, "tell me every time
> <function> gets called in this process", for a bunch of processes.
> 

I have used LTTng [1] extensively for profiling hal and udev on the N800
and its been very useful for me. Out of the box it can help you profile
when system calls happen, and you can add new events which you can emit
from user space [2]. The graphical tools need some love but the
information you get is very very useful. I heard at FOSDEM that the
future involves combining LTTng and SystemTap, which would rock my world ;)

Thanks,
Rob Taylor
Codethink Ltd.

[1] http://ltt.polymtl.ca/
[2] http://ltt.polymtl.ca/svn/ltt-usertrace/README