Ubuntu-MATE 15.10 is slow sometimes

Hi everyone!

2 weeks ago i installed Ubuntu MATE 15.10 and everything is working fine except that whole system can be slow sometimes. I think it have something to do with GPU. I have Radeon HD 5450 graphics card and it works fine in Windows.

First i installed fglrx drivers and system was working ok but 1080p video didn’t but it should. Later that day i removed fglrx drivers and i installed some opensource drivers and 1080p was working just fine but i had a feeling that whole OS is running slower at some moments.

Can anyone give me some helpful advice?

P.S. Here is fglrxinfo output and lshw output

lshw output: http://pastebin.com/S633vXQS

fglrxinfo
display: :0.0 screen: 0
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: AMD Radeon HD 5450
OpenGL version string: 4.5.13399 Compatibility Profile Context 15.201.1151

Have you tried disabling compositing ?
mate-tweak / window / compositing
trie lowering swappiness - instructions here
how mutch fps do you get in glxgears ?

Is your CPU overheating and therefore throttling itself?

I’ve measured CPU temperature with sensors console app and it’s arround 65C - 80C at full load using stress tool “stress -c 4”
temp2: +80.0°C (low = +127.0°C, high = +127.0°C) sensor = thermal diode

And this is glxgears output:
glxgears
587 frames in 5.0 seconds = 117.033 FPS
1482 frames in 5.0 seconds = 296.272 FPS
1427 frames in 5.0 seconds = 285.370 FPS
1405 frames in 5.0 seconds = 280.432 FPS
1353 frames in 5.0 seconds = 270.344 FPS
1082 frames in 5.0 seconds = 215.219 FPS
910 frames in 5.0 seconds = 181.224 FPS
1005 frames in 5.0 seconds = 199.844 FPS