User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b8pre) Gecko/20101201 Firefox/4.0b8pre Build Identifier: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b8pre) Gecko/20101201 Firefox/4.0b8pre Mozilla's HWACCEL demo is much slower for me with layers.accelerate-all on than with layers.accelerate-all off. I get ~15 FPS with layers.accelerate-all on and ~90 FPS with layers.accelerate-all off. Other websites demonstrate a similarly drastic slowdown as well. Reproducible: Always Steps to Reproduce: 1. Toggle layers.accelerate-all 2. Restart Firefox 3. Observe speed difference Actual Results: Compositing is much slower than XRENDER acceleration Expected Results: Compositing should match or exceed XRENDER acceleration in speed I am using a nightly from Dec. 2. I have a GeForce GTX 285 with nvidia blob 260.19.21 drivers. I am using a current ArchLinux installation with kernel 2.6.36.