[cairo] Re: On recovery from errors in cairo (was: cairo reset)

Mike Emmel mike.emmel at gmail.com
Tue Sep 26 08:37:59 PDT 2006

On 9/25/06, Kalle Vahlman <kalle.vahlman at gmail.com> wrote:
> 2006/9/25, Mike Emmel <mike.emmel at gmail.com>:
> [snap]
> > I've seen a lot of traffic on arm issues thats why I mentioned it.
> > I just can't give numbers for the device I'm testing but most arm
> > devices that use similar cpu's have about the same performance so
> > it does not matter too much.
> There's a lot of other variables that might kill the performance, for
> example the 770 suffers a lot from slow userspace-to-framebuffer
> transfers. My little (animated) cairo test mistakenly drew directly on
> the X11 surface (ie. window) at first and was dog slow, even though
> it's pretty simple in structure. When I converted it to use a
> backbuffer and only transferring areas that changed, the speed grew
> exponentially. Admittedly the backbuffering helped on my laptop too,
> but far less in comparison.

Hmm this may be a X11 problem generally I've seen the reverse.
Drawing to vram is fast since its on chip whild main memory to vram
transfers are dog slow since many devices are crippled with a 16bit bus.
This is changing but the main memory bus is almost always still slow compared
to desktop.  I'm guessing that for some reason there something wrong
with the xserver/render implementation on the device.

This is of course a place where using my directfb backend for direct access
is handy :)

 I'd suggest trying to include a symbian base cairo port in the
testing I' would be easy for somone from the frozen north to get cairo
up and running on symbian and it would give you a broader range of
devices to test.
I've not looked at the symbian port of webkit it may already use cairo.

> > Maybe someone from intel will send him a xscale device...
> We had a PXA290 at GUADEC and since our original demo ideas were
> failing (due to driver problems), I ran the same Cairo demo there and
> it was pretty good (this was before any of the real performance work
> put to Cairo). The PXA290 is of course from the higher end and beats
> 770 by far in numbers so it wasn't a big surprise really.
> But it was fun :)
I figured but the PXA290 is a nice cpu esp for power. The xscales where great
for demos but are just now getting decent battery life they are still
a power hog
I think I'm getting off topic :)

> --
> Kalle Vahlman, zuh at iki.fi
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