I have two identical video cards (Nvidia GTX 560) and four identical monitors (LG model E2240TI), all four arranged horizontally. I have gnome-session-flashback installed and am using the Gnome-flashback (Metacity) choice at login, though I don't think that matters, as using Gnome-flashback (Compiz) is almost as bad (though in slightly different ways).
Every 10 or 20 s (but not consistent), my mouse pointer freezes for 1 or 2 s. The mouse is the most noticeable but in fact all screen updates are frozen during these times (based on a "top -d 0.5" I have running).
Also (100% consistent) when moving mouse from screen 1 to 2, and from 4 to 3, the mouse disappears for about 3 to 4 s, (but never (!) when going the reverse direction 2 to 1, nor 3 to 4, nor either direction between 2 and 3). Also mouse "tracking" is still live during this time, just not shown (if I start this near the top of the screens, and during the "disappeared" time I move my mouse significantly downward, then when the mouse reappears, it is downward of the starting position by the expected amount).
Also when dragging a window, the mouse and window freeze almost immediately for about 4 s, then the window only moves jumpily and with 2 to 5 s gaps in updates (though the mouse itself moves smoothly during this time), and CPU usage of Xorg process goes to 99% during this time.
Also just wiggling the mouse rapidly in a circle over a terminal window (in which top is running), the CPU usage of Xorg also goes to 99% (yet doing the same over blank desktop area I cannot get it over 8%).
Also when clicking to change windows, the newly selected window will come to the front immediately but will not get focus for about 4 s ("focus" based on colour change of title bar, terminal cursor change from outline to solid, accept typed characters, etc).
I have two identical video cards
# lspci |grep VGA
01:00.0 VGA compatible controller: NVIDIA Corporation GF114 [GeForce GTX 560 Ti] (rev a1)
02:00.0 VGA compatible controller: NVIDIA Corporation GF114 [GeForce GTX 560 Ti] (rev a1)
I am using the nouveau driver:
# lsmod |grep -i nouveau
nouveau 1388544 4
video 36864 2 nouveau,asus_wmi
i2c_algo_bit 16384 1 nouveau
ttm 94208 1 nouveau
drm_kms_helper 126976 1 nouveau
mxm_wmi 16384 1 nouveau
drm 356352 7 ttm,drm_kms_helper,nouveau
wmi 20480 3 mxm_wmi,nouveau,asus_wmi
My xrandr output is as follows. I don't understand much about providers, or source versus sink, but I suspect that may be the way to make sure rendering load is actually spread across the video cards. Again I haven't been able to find the nitty gritty of xrandr, although I did used to play with xrandr precise timings (mode lines) back in the ubuntu 10.04 and 12.04 days when it wouldn't by default see my projector (different box).
$ xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x97 cap: 0x1, Source Output crtcs: 2 outputs: 4 associated providers: 1 name:nouveau
Provider 1: id: 0x45 cap: 0x6, Sink Output, Source Offload crtcs: 2 outputs: 4 associated providers: 1 name:nouveau
$ xrandr
Screen 0: minimum 320 x 200, current 7680 x 1080, maximum 8192 x 8192
DVI-I-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.00*+
1680x1050 59.88
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00
720x400 70.08
DVI-I-2 connected 1920x1080+5760+0 (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.00*+
1680x1050 59.88
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00
720x400 70.08
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DVI-I-1-3 connected 1920x1080+1920+0 477mm x 268mm
1920x1080 60.00*+
1680x1050 59.88
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00
720x400 70.08
DVI-I-1-4 connected 1920x1080+3840+0 477mm x 268mm
1920x1080 60.00*+
1680x1050 59.88
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00
720x400 70.08
HDMI-1-2 disconnected
DP-1-2 disconnected
1920x1080 (0x46) 148.500MHz
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.50KHz
v: height 1080 start 1084 end 1089 total 1125 clock 60.00Hz
1680x1050 (0x47) 119.000MHz
h: width 1680 start 1728 end 1760 total 1840 skew 0 clock 64.67KHz
v: height 1050 start 1053 end 1059 total 1080 clock 59.88Hz
1280x1024 (0x48) 135.000MHz
h: width 1280 start 1296 end 1440 total 1688 skew 0 clock 79.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 75.02Hz
1280x1024 (0x49) 108.000MHz
h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz
1152x864 (0x4a) 108.000MHz
h: width 1152 start 1216 end 1344 total 1600 skew 0 clock 67.50KHz
v: height 864 start 865 end 868 total 900 clock 75.00Hz
1024x768 (0x4b) 78.800MHz
h: width 1024 start 1040 end 1136 total 1312 skew 0 clock 60.06KHz
v: height 768 start 769 end 772 total 800 clock 75.08Hz
1024x768 (0x4c) 65.000MHz
h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz
v: height 768 start 771 end 777 total 806 clock 60.00Hz
800x600 (0x4d) 49.500MHz
h: width 800 start 816 end 896 total 1056 skew 0 clock 46.88KHz
v: height 600 start 601 end 604 total 625 clock 75.00Hz
800x600 (0x4e) 40.000MHz
h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz
v: height 600 start 601 end 605 total 628 clock 60.32Hz
640x480 (0x4f) 31.500MHz
h: width 640 start 656 end 720 total 840 skew 0 clock 37.50KHz
v: height 480 start 481 end 484 total 500 clock 75.00Hz
640x480 (0x50) 25.200MHz
h: width 640 start 656 end 752 total 800 skew 0 clock 31.50KHz
v: height 480 start 490 end 492 total 525 clock 60.00Hz
720x400 (0x51) 28.320MHz
h: width 720 start 738 end 846 total 900 skew 0 clock 31.47KHz
v: height 400 start 412 end 414 total 449 clock 70.08Hz
I don't think this is a duplicate of Ubuntu 15.04 freezes for a second every 6-10 seconds, PCI/Radeon related messages in kern.log since there is nothing in my /var/log/kern.log (nor any other logs) when this happens. Also this Four monitor setup with two Nvidia graphics cards doesn't seem relevant as it is from 3 years ago (and ubuntu 12.04), and is for the proprietary nvidia driver.
Any tips on getting this to work somewhat reasonably? Mahjongg is completely unusable in this state.
p.s. logging in with Gnome flashback (Compiz) instead of ...(Metacity), is just as bad but different. CPU use by Xorg doesn't go much above 10% regardless of whether wiggling the mouse over blank desktop area, over a terminal window, or while dragging a window. However stuff freezes up even more often, every 1 or 2 s, and lasts 1 or 2 s, on screens 1 and 4, and not at all (!) on screens 2 and 3. Logging in with Gnome default (which is Compiz and the Unity interface) is also just as bad but in slightly different ways. Also in all three session types, the problems go away if I use the System Settings > Displays to disable all but the first screen.