[drm:i965_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
The line is colored in red and this is not good for your system, because your graphic card have poor performance (in some cases glitches or worst, frozen system). The reason of this is the method of graphic acceleration used by Intel on a graphic card. Nowadays, Intel is using three methods of graphic acceleration in Linux:
1.- UXA
2.- SNA
3.- Glamor
UXA is not obsolete but is antique. SNA is stable and modern. Glamor is newer but is still in development. The method of graphic acceleration used by default in Debian 9 (Stretch) is Glamor... and this is the problem. To fix this, we need change the method of graphic acceleration used by default (Glamor) to SNA.
How to fix? Let's go.
STEPS:
Open a terminal and type:
$ cd /
$ cd usr/share/X11/xorg.conf.d/
$ sudo pluma 20-intel.conf
NOTE: I'm using pluma text editor because I have MATE Desktop installed on my system, but you can use your favorite text editor (nano, vim, etc.)
In these file just write this:
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "AccelMethod" "sna"
EndSection
Save and exit.
$ sudo reboot
That's all.
Tuxkernel...
UPDATE:
To see the performance of your graphic card install gtkperf. Open a terminal and type:
$ sudo apt-get install gtkperf
Then go to Applications > System > gtkperf
And do two or three testings.
My testings:
Using glamor:
9.80 seconds (one)
9.93 seconds (two)
Using SNA:
4.67 seconds (one)
4.69 seconds (two)
Remember, less is better.
UPDATE 2-March-2020:
For Toshiba Satellite L305-SP6912R, open a terminal and type:
$ cd /
$ sudo pluma etc/default/grub
Add loglevel=3 option. Example:
GRUB_CMDLINE_LINUX_DEFAULT="quiet usbhid.quirks=0x1D57:0xFA0A:0x20000000 usbhid.mousepoll=1 loglevel=3"
Save and exit.
$ sudo update-grub
$ sudo update-grub2
$ sudo reboot
That's all.
Tuxkernel...
