[Maxima] computation time information

[Eric Reyssat]

Hello,

I would like to compare the time complexities of some functions that I 
defined with Maxima. Is there a better way to collect the times than

showtime:true;
f(1);
f(2);
f(4);
...
f(2^30);

and then copy-paste-clean "by hand" Maxima's results ?
Is the output given by showtime, or any other time information, 
available in some variables ?

Eric Reyssat