[webkit-dev] Parallel image decoders are up for review

KwangYul Seo skyul at company100.net
Tue Jul 17 01:49:42 PDT 2012

Thank you letting me know this information!

On Tue, Jul 17, 2012 at 5:41 AM, Alpha Lam <hclam at chromium.org> wrote:

> Hi!
> This is great work!
There's work in the Chromium port going on that has a similar goal as your
> parallel image decoding effort. There are some parts that we overlap that I
> think should be discussed to avoid clashes.
What's  the current progress of Chromium work? Can I check out the source
code? Do you have a design document?

Here's some background information of what we're doing. In Chromium port
> there's a deferred painting mode that we record painting commands and
> playback (rasterize) on another thread. Recording on the main thread
> requires images to be synchronously decoded and our current focus is to
> defer image decoding to a later time and eventually have parallel image
> decoding.
> The specific part we overlap is drawing an asynchronously decoded
> BitmapImage to GraphicsContext. Your patch does the whole image decoding
> asynchronously while we just care about whether an image can be
> asynchronously decoded or not. This part in particular I think we should
> discuss to make sure we're both comfortable with.

Our approach also checks if the given image can be decoded asynchronously
or not. Please refer to "3.3 Criteria to Use Parallel Image Decoders" of
our design document. (

I certainly want to hear more about your approach here.

> I'll make a few comments on the patch in the webkit bug.
Thanks. I think we can improve both approaches by sharing ideas with each
other regarding asynchronous image decoding because they have much in

Thanks and this is great effort!
> Alpha
> 2012/7/9 KwangYul Seo <skyul at company100.net>
>> Hi,
>> Our team at Company 100 has worked on parallel image decoders for past a
>> few weeks and some patches are pending for review now. Here is the master
>> bug for parallel image decoders:
>> https://bugs.webkit.org/show_bug.cgi?id=90375
>> For the overall architecture and design, please refer to the following
>> design document. We will update the design document as we change code after
>> review.
>> https://docs.google.com/document/pub?id=12gf7MhNHfupeR3GdRF-h2Vzg86viCbwXq8_JByHKlg0
>> Our implementation shows considerable speedup in image intensive sites
>> and no performance regression in PLT. Please refer to the master bug for
>> specific numbers.
>> We do understand many paralleization techniques make code so complex to
>> the level that can't be accepted. So we tried our best to reduce the
>> complexity of code, but reviewers can help us reduce it further.
>> Regards,
>> Kwang Yul Seo
>> _______________________________________________
>> webkit-dev mailing list
>> webkit-dev at lists.webkit.org
>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
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