ports/183435: x11/xorg: 100% CPU use of xorg using firefox when showing large images (say 20 Mpixel)

[Photo stuff]

The following reply was made to PR ports/183435; it has been noted by GNATS.

From: Photo stuff <w-info2 at xs4all.nl>
To: Callum Gibson <callumgibson at optusnet.com.au>, bug-followup at FreeBSD.org
Cc:  
Subject: Re: ports/183435: x11/xorg: 100% CPU use of xorg using firefox when
 showing large images (say 20 Mpixel)
Date: Tue, 10 Dec 2013 10:24:49 +0100

 On 12/02/13 04:17, Callum Gibson wrote:
 > You might find this is related to pixmap caching. I don't think it's
 > video driver specific.  Ironically the variable to disable this is called:
 > MOZ_DISABLE_IMAGE_OPTIMIZE
 >
 > https://wiki.mozilla.org/Mobile/MemoryReduction#Disable_X_image_caching_on_Unix.2FLinux
 >
 > Maybe at some time in the past with smaller images and slower networks
 > it hurt performace, but now displaying large, modern images in firefox causes
 > it to stuff an enormous pixmap into the X server which is used once, and
 > eats all the CPU whilst firefox is just hanging there waiting for it to finish.
 > Setting this variable fixes it for me.
 
 
 I didn't have this issue until FreeBSD 9.2 (9.1RC1 was OK for example, 
 although that was with i386 and 1GB RAM, now I use amd64 and 8GB RAM). 
 So something must have changed somewhere (in the Xorg drivers or 
 Mozilla) relatively recently.
 
 I got another suggestion a while ago from Mr. S. Farley, namely to set 
 gfx.xrender.enabled to false.
 
 This works...
 
 After your email I have tested MOZ_DISABLE_IMAGE_OPTIMIZE=1 as in that 
 link, instead of gfx.xrender.enabled, and that works too. Strangely when 
 I set the variable to 0 it also works so the value doesn't seem to be 
 used, and rechecking with the environment variable removed indeed the 
 issue is back.
 
 Searching for both these keywords (MOZ_DISABLE_IMAGE_OPTIMIZE and 
 gfx.xrender.enabled) I found:
 
 http://comments.gmane.org/gmane.os.openbsd.ports/61076
 
 I don't know anything about the nvidia drivers nor the Mozilla source 
 and how they arrange memory use, so I can't be of much help to narrow 
 down the issue.
 
 What I also have btw, which is mentioned on that gmane.org page, is that 
 I sometimes 'play' with the mouse while reading text, select text and 
 when I let go somewhere else, the whole text is shown moving back to the 
 original position. I don't see the point in this, but it's also 
 something that can slow everything to a halt. This I encountered quite a 
 while ago, not sure exactly when.
 
 
 On the ports mailing list I found the problem too after looking for the 
 above 2 keywords:
 
 http://lists.freebsd.org/pipermail/freebsd-ports/2013-March/081767.html
 
 Some people don't have the problem, others do. So possibly a driver 
 issue? (Note that I have an nvidia card, some of the comments I read of 
 problems were from nvidia users)
 
 Wouter