Re: Tab switching "feels" slower in epiphany than in firefox

[Federico Mena Quintero <federico ximian com>]

On Tue, 2006-10-24 at 18:39 +0200, Lucas Nussbaum wrote:

> What I reported back then is that switching between tabs in epiphany
> "felt" a lot slower than in firefox. The problem only appeared when
> using the 'ati' driver with the PCI card (which can be assumed to be
> slow, even if it's quite recent). It wasn't noticeable when using the
> fglrx driver with the laptop's internal video card.

I just ran Sysprof and did this:

1. open 5 tabs in Epiphany, with different pages (three bugzilla bugs,
one wiki page, one page with a big image).

2. Start sysprof.

3. Hit Alt-[12345] to switch to the tabs many times.

4. Stop sysprof.

It's spending 35% of the time in fontconfig, and 17% in the X server's
libfb.  I have xorg-x11-6.9.0-50.14 from SLED 10, on a Thinkpad T41p
(that's an ATI Radeon, I think).

> So, my questions are:
> - is this a known problem ?

No, thanks for reporting it :)

> - whose fault (component-wise) is it ? (I'm not really familiar with
>   GNOME development)

I'd look at what fontconfig is doing.  I don't know if it's also the
slowest part of your setup.  Unfortunately, I don't have a debug build
of fontconfig on my machine, so I can't tell what is going on inside the
library.

> - what are the likely causes for this ?

Ask the profiler!

> - is this going to be improved ?

Only if someone cares enough about it.  Want to give it a try? :)

> Others related questions:
> - are people working on benchmarking the gnome frameworks with slow
>   hardware ?

Yes, Nokia is working hard on making GNOME (well, Maemo) run on the
Nokia 770, which is a slow ARM processor with little RAM.  You'll also
see good stuff come out of OLPC.

> - Are there software tools to help diagnose such issues ? (based on
>   traces analysis maybe ?)

Yes.  Please see http://live.gnome.org/GnomePerformance 

Also, read the report from my Summer of Code student:
http://m3gumi.wordpress.com/2006/08/31/report/

Cecilia added code to Evolution to get timings on how long it takes to
switch between Evolution's components.  By plotting the timings and then
running sysprof, she was able to find the root of the problem.  You
could do something similar to find the problem in Epiphany, by adding
code to give you timings on how long it takes to switch between tabs.

> - Are there software tools allowing to emulate a slower video card to
>   make the detection of such issues easier ?

Not that I know of.

  Federico