Re: GdkPixbufLoader vs. _from_file: speed issue

[Matthias Clasen <mclasen redhat com>]

On Wed, 2005-08-24 at 17:59 +0200, Nicolas George wrote:
> I am trying to load an image, and I am comparing two methods: a plain
> gdk_pixbuf_new_from_file, and a GdkPixbufLoader with a
> fread/gdk_pixbuf_loader_write loop. I am very surprised by the difference of
> efficiency of both methods: with my sample image, on the computer I am
> using, gdk_pixbuf_new_from_file takes only about 3.5 seconds, while the
> GdkPixbufLoader method takes about 22 seconds. I understand that keeping
> track of the current state and keeping the data structure consistent across
> calls must take some time, but I expected a 10% cost, not a 500% cost!
> 
> To have things right, here are some details:
> 
> - There is no swap/out of memory problems, all is well within the cache and
>   free memory limit, and the limiting factor is really CPU.
> 
> - Almost all the time is spent in gdk_pixbuf_loader_write. In particular, I
>   am not wasting time in the loop system since all the file is read in just
>   4 big fread.
> 
> - There is no signal for area-updated; adding a no-op one costs two more
>   seconds.
> 
> - It is a Gtk+ 2.6.8-1 from Debian, on a Pentium 266. I did not find
>   anything pertinent in the ChangeLog to expect better with 2.8.1.
> 
> I intended to use a GdkPixbufLoader to do partial rendering while loading a
> big image, but if it means that the user must wait six times what he would
> have waited otherwise, it is somewhat defeating the purpose.
> 
> Did I miss something?

That sounds wrong. Can you post your benchmark ?