gnome-shell assume a CPU

Question

Eu tenho o Debian 8.5 com o desktop gnome. Muitas vezes o gnome-shell está usando a CPU acima de 70% (às vezes acima de 100%). Por que isso está acontecendo? principalmente até agora quando eu executo um projeto de python-pygame O uso de CPU do gnome-shell vai além de 100% e o jogo roda muito devagar.

Editar

Esse uso da CPU acontece mesmo quando eu pego uma janela e a movo! Mesmo isso causa mais de 100% de uso da CPU pelo gnome-shell. Alguém pode ajudar?

Aqui estão algumas saídas de terminal:

lspci | grep -i --color vga
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09)

lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 61
Model name:            Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
Stepping:              4
CPU MHz:               2613.359
CPU max MHz:           2700.0000
CPU min MHz:           500.0000
BogoMIPS:              4389.85
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              3072K
NUMA node0 CPU(s):     0-3


amir@amir-debian:~$ sudo lshw -short
H/W path        Device     Class          Description
=====================================================
                           system         Computer
/0                         bus            Motherboard
/0/0                       memory         7703MiB System memory
/0/1                       processor      Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
/0/100                     bridge         Broadwell-U Host Bridge -OPI
/0/100/2                   display        HD Graphics 5500
/0/100/3                   multimedia     Broadwell-U Audio Controller
/0/100/14                  bus            Wildcat Point-LP USB xHCI Controller
/0/100/14/0     usb3       bus            xHCI Host Controller
/0/100/14/1     usb2       bus            xHCI Host Controller
/0/100/14/1/5              generic        EMV Smartcard Reader
/0/100/14/1/6              generic        Generic USB device
/0/100/14/1/7              communication  Bluetooth wireless interface
/0/100/14/1/8              multimedia     Integrated Camera
/0/100/16                  communication  Wildcat Point-LP MEI Controller #1
/0/100/19       eth0       network        Ethernet Connection (3) I218-LM
/0/100/1b                  multimedia     Wildcat Point-LP High Definition Audio Controller
/0/100/1c                  bridge         Wildcat Point-LP PCI Express Root Port #6
/0/100/1c/0                generic        RTS5227 PCI Express Card Reader
/0/100/1c.1                bridge         Wildcat Point-LP PCI Express Root Port #3
/0/100/1c.1/0   wlan0      network        Wireless 7265
/0/100/1d                  bus            Wildcat Point-LP USB EHCI Controller
/0/100/1d/1     usb1       bus            EHCI Host Controller
/0/100/1d/1/1              bus            USB hub
/0/100/1f                  bridge         Wildcat Point-LP LPC Controller
/0/100/1f.2                storage        Wildcat Point-LP SATA Controller [AHCI Mode]
/0/100/1f.3                bus            Wildcat Point-LP SMBus Controller
/0/100/1f.6                generic        Wildcat Point-LP Thermal Management Controller
/0/2            scsi0      storage        
/0/2/0.0.0      /dev/sda   disk           256GB SAMSUNG MZ7LN256
/0/2/0.0.0/1    /dev/sda1  volume         9536MiB EXT4 volume
/0/2/0.0.0/2    /dev/sda2  volume         229GiB Extended partition
/0/2/0.0.0/2/5  /dev/sda5  volume         9346MiB Linux swap / Solaris partition
/0/2/0.0.0/2/6  /dev/sda6  volume         220GiB Linux filesystem partition