[Webkit-unassigned] [Bug 90375] Parallel image decoders

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=90375





--- Comment #84 from Huang Dongsung <luxtella at company100.net>  2012-08-16 02:17:50 PST ---
(In reply to comment #83)
> So, if I understand correctly, in these cases the number of decoded images in the cache could be a lot higher, so the slow rendering could be replaced by an out of memory error on embedded devices. Perhaps it would be better to disable parallel decoding.

Yes. Bug 90721 can cause OOM on embedded devices as you concerned, but this patch is a image decoding policy change regarding space-time trade-offs. It applies equally to the current serial image decoding as well as parallel image decoding. Parallel image decoder does not spend more memory because of this patch.

Previously, the memory cache caused repeated image decoding when the cache capacity of MemoryCache is exceeded. Animation and scrolling could slow down dramatically because both could trigger image decoding every frame. Bug 90721 fixed this behavior by preventing decoded images inside the viewport from being destroyed. You can argue on this behavior change, but it is not directly relevant to parallel image decoding.

It is true that parallel image decoder spends more space; kernel objects to run more threads and temporary data used to transfer encoded and decoded data between the main thread and decoder threads. If you want to save these additional memory consumption on embedded devices, you can turn off parallel image decoder.

Currently, MemoryCache removes only the decoded data of live caches. If the size of encoded data of cached images is big enough, WebKit on embedded devices still can throw an OOM error. We need a more sophisticated policy to handle this situation.

-- 
Configure bugmail: https://bugs.webkit.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.