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Riccardo Magrini
Asked: 2014-12-24 14:58:43 +0800 CST

Why qemu-system-x86 takes 100% of my CPU?

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I've changed my old laptop with a new one but I don't understand why using on both virt-manager the qemu-system-x86 on new one takes 100% of CPU when run a vm, while on old one not.

The command:

lscpu

has this output:

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:                 69
Stepping:              1
CPU MHz:               754.000
BogoMIPS:              5187.74
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              4096K
NUMA node0 CPU(s):     0-3

While in my old PC it just uses 15%-30% of the CPU. I've also actived the kvm from the BIOS but nothing changes: it continues to use 100%.

The top command gives me:

PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
3410 libvirt+  20   0 3641892 902428  10332 S 101,4 11,2   1:03.36 qemu-system-x86

How should I proceed?

kvm

2 Answers

  1. Have you tried to make sure you use the proper accelaration for qemu?
    Such as: 

    qemu-system-x86_64  -machine accel=kvm [...]

    This switch could make your computer use hardware virtualization
    (cpu usage drops to negligible then)

    • 3

  2. I've resolved that modify an option on BIOS,after that now CPU uses just 20%.

    • -8