System freezes for for mins and i have switch terminal to get back

Hi Team,

system totally freezes and will not able to access anything. Below logs tells something but i have no idea about it. Please let me know if anything i have done wrong.

Jul 30 18:52:34 DevOps kernel: [ 9176.747361] nouveau 0000:03:00.0: DRM: resuming kernel object tree...
Jul 30 18:52:34 DevOps kernel: [ 9176.859911] nouveau 0000:03:00.0: bus: MMIO write of 0000001f FAULT at 6013d4 [ IBUS ]
Jul 30 18:52:34 DevOps kernel: [ 9176.860495] nouveau 0000:03:00.0: DRM: resuming client object trees...
Jul 30 18:52:34 DevOps systemd[1]: Started Getty on tty2.
Jul 30 18:52:39 DevOps kernel: [ 9181.978689] ACPI Warning: \_SB_.PCI0.RP05.PEGP._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20150930/nsarguments-95)
Jul 30 18:52:39 DevOps kernel: [ 9181.979044] ACPI: \_SB_.PCI0.RP05.PEGP: failed to evaluate _DSM
Jul 30 18:52:39 DevOps kernel: [ 9181.979051] ACPI Warning: \_SB_.PCI0.RP05.PEGP._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20150930/nsarguments-95)
Jul 30 18:52:39 DevOps kernel: [ 9181.979276] nouveau 0000:03:00.0: DRM: evicting buffers...
Jul 30 18:52:39 DevOps kernel: [ 9181.979279] nouveau 0000:03:00.0: DRM: waiting for kernel channels to go idle...
Jul 30 18:52:39 DevOps kernel: [ 9181.979325] nouveau 0000:03:00.0: DRM: suspending client object trees...
Jul 30 18:52:39 DevOps kernel: [ 9181.979770] nouveau 0000:03:00.0: DRM: suspending kernel object tree...
Jul 30 18:52:49 DevOps systemd[1]: Started Session 3 of user vadiraj.

+++++++++++++++++++
vadiraj@DevOps:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.1 LTS
Release: 16.04
Codename: xenial
vadiraj@DevOps:~$ uname -a
Linux DevOps 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
vadiraj@DevOps:~$

Thanks for all your helps!!!.

Regards,
Vadiraj