User Agent: Mozilla/5.0 (Windows NT 6.1; rv:34.0) Gecko/20100101 Firefox/34.0 (Beta/Release) Build ID: 20140826030203 Steps to reproduce: Open latest FireFox Nightly => about:addons Actual results: When scrolling the *page hangs*. See screenshot. High CPU Expected results: Smooth and easy scroll, low CPU

Could you paste Graphics section of about:support?

Graphics Adapter Description NVIDIA GeForce 8200M G Adapter Drivers nvd3dum nvwgf2um,nvwgf2um Adapter RAM 256 Device ID 0x0845 Direct2D Enabled true DirectWrite Enabled true (6.2.9200.16571) Driver Date 7-2-2014 Driver Version 9.18.13.4052 GPU #2 Active false GPU Accelerated Windows 2/2 Direct3D 11 (OMTC) Subsys ID 360a103c Vendor ID 0x10de WebGL Renderer Google Inc. -- ANGLE (NVIDIA GeForce 8200M G Direct3D9Ex vs_3_0 ps_3_0) windowLayerManagerRemote true AzureCanvasBackend direct2d AzureContentBackend direct2d AzureFallbackCanvasBackend cairo AzureSkiaAccelerated 0

Setting layers.offmainthreadcomposition.enabled to false + restart makes the issue disappear.

Seems fixed in latest Nightly but still high CPU when scrolling.

(In reply to Peter Kroon from comment #4) > still high CPU when scrolling. only with omtc enabled?

(In reply to Paul Silaghi, QA [:pauly] from comment #5) > (In reply to Peter Kroon from comment #4) > > still high CPU when scrolling. > only with omtc enabled? When enabled 100% When disabled 50/60%

i can't even open about:addons in ff40, filed Bug 1189192

seems to be an old bug no current version seems affected anymore

Can't reproduce in current Nightly: 52.0a1 (2016-09-25) (64-bit) Can't reproduce in current stable: 49.0.1 Appears to have been fixed on Windows 10 64 BIT. Not sure about Windows 7 and Linux.

Can't reproduce anymore. Closing bug.