WebKit meeting next week and rendering

Lately I’ve been checking the rendering code in WebKitGTK+, graphics are always very challenging. We want to check how to improve scrolling and rendering in general. Maybe some of the points are interesting for someone else or maybe you can send me some feedback about them:

  • I’ve used cairo-trace and cairo-perf-trace to check the performance of different backends doing a usual short browsing session (open slashdot and scroll) with Epiphany. I wanted to add Skia to the test because I wanted to compare with Chrome backend. Cairo Skia backend does not look well maintained, I had to change some code in order to compile it, but it worked eventually. The results are interesting because shows that Xlib backend is faster (probably accelerated operations) than Skia and Skia is a little bit faster than the Cairo image backend but quite similar, both probably running on the CPU:
    [ # ]  backend                         test   min(s) median(s) stddev. count
    [  0]     null                     epiphany    0.644    0.652   2.06%    6/6
    [  0]       gl                     epiphany    7.121    8.770   8.91%   15/15
    [  0]     skia                     epiphany    2.106    2.110   0.11%    5/6
    [  0]     xlib                     epiphany    1.874    1.903   1.41%    5/6
    [  0]    image                     epiphany    2.154    2.180   1.09%    6/6
    [  0]  image16                     epiphany    3.721    3.752   0.59%    6/6

    If this is correct we have to look inside WebKit for improvements, which means we have to review the rendering process carefully.

  • After checking the patches for the tiled backing store I’ve implemented a tiled backing store for WebKitGTK+ in a branch of a local repository in Igalia. It still has some pending work (graphic context not correctly used in forms, frames are not supported, threading, resizes, etc.). Results regarding performance are not the expected ones but it works and we can check the performance, conclusion is still not clear, blit is fast but we need to improve the tiles rendering. I think we have to be very sure that we are improving the situation when adding complex code, so there is still work here to show it makes sense.

I would like to add that cairo-trace is an awesome tool, Cairo people deserve a lot of kudos for implementing it. I will use cairo-trace to check the tiled backing store and how the solution of the form controls rendering behaves with regard to performance.

Regarding the other part of the topic, next week some of us will be in San Francisco for the Webkit meeting, we will also attend the Linux Collaboration Summit and meet some people there; so if you are in the bay area and you want to have a drink just sent us an email. With the last WebKit2 announcement I think it would be a very interesting meeting.

I almost forgot, our WebKit team in Igalia has grown and we have more motivated people working with us (currently Xan, Philippe, Sergio, Mario, Juanjo and me, and Diego doing his internship), this is good because we could work in more interesting topics inside the project.

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