I recently switched from NVidia to Nouveau driver, on a dual-head Gentoo AMD64
computer.

Only with Google Maps on Firefox (version 45, 46 or 49), the 'default' maps
loads ok but anything that would require to redisplay the map's tiles leads
quickly to total freeze of the computer. 

 Xorg.0.log file contains several error backtraces :

(EE) [mi] EQ overflowing.  Additional events will be discarded until existing
events are processed.
(EE) 
(EE) Backtrace:
(EE) 0: /usr/bin/X (xorg_backtrace+0x56) [0x589e96]
(EE) 1: /usr/bin/X (mieqEnqueue+0x24b) [0x56bddb]
(EE) 2: /usr/bin/X (QueuePointerEvents+0x52) [0x44db52]
(EE) 3: /usr/lib64/xorg/modules/input/evdev_drv.so (0x7fd526d53000+0x623f)
[0x7fd526d5923f]
(EE) 4: /usr/lib64/xorg/modules/input/evdev_drv.so (0x7fd526d53000+0x6acd)
[0x7fd526d59acd]
(EE) 5: /usr/bin/X (0x400000+0x74ea8) [0x474ea8]
(EE) 6: /usr/bin/X (0x400000+0x99da7) [0x499da7]
(EE) 7: /lib64/libc.so.6 (0x7fd53212e000+0x332d0) [0x7fd5321612d0]
(EE) 8: /lib64/libc.so.6 (ioctl+0x5) [0x7fd53220f825]
(EE) 9: /usr/lib64/libdrm.so.2 (drmIoctl+0x28) [0x7fd5332bfc68]
(EE) 10: /usr/lib64/libdrm.so.2 (drmCommandWrite+0x1b) [0x7fd5332c298b]
(EE) 11: /usr/lib64/libdrm_nouveau.so.2 (nouveau_bo_wait+0xbc) [0x7fd52da9743c]
(EE) 12: /usr/lib64/xorg/modules/drivers/nouveau_drv.so (0x7fd52dc9c000+0x7f2d)
[0x7fd52dca3f2d]
(EE) 13: /usr/lib64/xorg/modules/libexa.so (0x7fd52d455000+0x586b)
[0x7fd52d45a86b]
(EE) 14: /usr/lib64/xorg/modules/libexa.so (0x7fd52d455000+0x7f70)
[0x7fd52d45cf70]
(EE) 15: /usr/lib64/xorg/modules/libexa.so (0x7fd52d455000+0x10c01)
[0x7fd52d465c01]
(EE) 16: /usr/bin/X (0x400000+0x114ea7) [0x514ea7]
(EE) 17: /usr/bin/X (0x400000+0x31a86) [0x431a86]
(EE) 18: /usr/bin/X (0x400000+0x3553f) [0x43553f]
(EE) 19: /usr/bin/X (0x400000+0x395b3) [0x4395b3]
(EE) 20: /lib64/libc.so.6 (__libc_start_main+0xf0) [0x7fd53214e620]
(EE) 21: /usr/bin/X (_start+0x29) [0x423919]
(EE) 
(EE) [mi] These backtraces from mieqEnqueue may point to a culprit higher up
the stack.
(EE) [mi] mieq is *NOT* the cause.  It is a victim.
(EE) [mi] EQ overflow continuing.  100 events have been dropped.

Hardware : 
02:00.0 VGA compatible controller: NVIDIA Corporation GF106M [GeForce GTX 460M]
(rev a1)

Software :
Kernel 4.1.15
xorg-server 1.18.4
nouveau driver 1.0.12