516594 - Reduce calls to IsLowMemory() from imagelib

Status: RESOLVED WONTFIX

(Core :: Graphics: ImageLib, defect)

Description

[Doug Turner (:dougt)]

Attachment: patch v.1

Turns out that calling IsLowMemory() can take as much as 2-4ms on some mobile platforms, and we call it alot from imglib.

I would like to reduce such calls -- maybe when we are writing less than 32k?

Comment 1

[Joe Drew (not getting mail)]

Comment on attachment 400616 [details] [diff] [review]
patch v.1

mSize.width * mSize.height * 4

Comment 2

[Doug Turner (:dougt)]

well, hell....

if I am seeing this makes a difference, that means what?  that we have lots of small images that are causing this much noise?  Maybe we should do a better job caching?  Fennec has a 1mb image cache.

Comment 3

[Joe Drew (not getting mail)]

Right now you're just comparing width * height, which is not a size in bytes, it's a size in pixels. If you want to use bytes, you have to multiply by 4.

Comment 4

[Doug Turner (:dougt)]

well, i see that now.  :-)

i suppose I am asking more a fundamental question.  basically my calculations were off by 4x.  which means that I am only filtering very very small images from this IsLowMemory check.  I am wondering why I am seeing a bunch of these when I am panning around in fennec.  eg. why aren't they cached / why are they being re-decoded.

Comment 5

[Doug Turner (:dougt)]

isLowMemory() is deprecated.  i removed these calls a while ago, so this patch isn't needed.