plymouth performance

[Daniel Drake]

Hi,

I've done some timings of plymouth vs non-plymouth boots on my XO
laptops, to see how much of an impact it has on boot time.

I took each measurement 3 times and then averaged. All recorded times
were without much variance; these timings were reliable.

I measured by pausing OFW during boot, entering "boot", and then
starting a stopwatch at the same time as pressing enter to execute the
boot command.
On the XO-1 I stopped the stopwatch as soon as I saw the mouse cursor
(just before gdm comes up).
On the XO-1.5 I stopped the stopwatch as soon as I saw the text at the
center of the gdm login screen.

For the "without" tests, I removed the rhgb kernel parameter parameter
and added console=tty0


On the XO-1:

Without plymouth: 61.53 seconds bootup time
With plymouth: 79.82 seconds bootup time
+18.29 seconds increase, or 30% regression


On the XO-1.5:

Without plymouth: 24.78 seconds bootup time
With plymouth: 27.07 seconds bootup time
+2.29 seconds increase, or 10% regression



We have a similar problem with OLPC's boot animation code on the XO-1.
We recently found out that it slows down boot by about 15 seconds with
just a simple animation.

However, two superheroes came along and implemented an awesome new
algorithm which only redraws the parts of the screen that have changed
from the last frame. This completely cuts out the 15-second regression
to the point where when you measure timings like the above tests, it
often appears that it is tiny bit faster to boot *with* the animation...
I wonder if that could be implemented in plymouth. The code is here:
http://dev.laptop.org/git/users/bobbyp/bootanim/

Daniel