CentOS 6.x High CPU usage in power_saving threads

Posted: 2015-07-29 09:02:08 by Alasdair Keyes

Direct Link | RSS feed


I was awoken at 3am this morning by a backup server complaining about high CPU... because these things never happen at a nice friendly time like 3pm Monday to Friday.

It looked that the kernel's power saving threads were using a lot of cpu on this CentOS 6.6 box.

# top

top - 08:40:21 up 84 days, 22:46,  1 user,  load average: 7.49, 7.51, 7.60
Tasks: 269 total,  14 running, 255 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us, 72.8%sy,  0.0%ni, 27.2%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  16249656k total,  2427188k used, 13822468k free,   185756k buffers
Swap:  4194300k total,        0k used,  4194300k free,  1523072k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                                                              
 2089 root      -2   0     0    0    0 R 100.0  0.0 359:08.11 power_saving/4                                                                                                                                      
 2086 root      -2   0     0    0    0 R 97.4  0.0 358:49.54 power_saving/1                                                                                                                                       
 2088 root      -2   0     0    0    0 R 97.4  0.0 358:55.72 power_saving/3                                                                                                                                       
 2085 root      -2   0     0    0    0 R 95.7  0.0 358:42.58 power_saving/0                                                                                                                                       
 2087 root      -2   0     0    0    0 R 95.7  0.0 359:00.27 power_saving/2                                                                                                                                       
 2090 root      -2   0     0    0    0 R 95.7  0.0 359:10.27 power_saving/5          

Stopping the acpid service didn't seem to help and the only thing that resolved the issue was to unload the acpi_pad module from the kernel. At which the power_saving threads were removed and the load dropped again.

# service acpid stop
Stopping acpi daemon:                                      [  OK  ]
# lsmod | grep acpi_pad
acpi_pad               87985  0 
# rmmod acpi_pad
# lsmod | grep acpi_pad
#

There is a Redhat advisory of a similar issue, but this indicates that it's only on CentOS 6.2, but it appears that it has continued into later revisions of the Redhat kernel.


If you found this useful, please feel free to donate via bitcoin to 1NT2ErDzLDBPB8CDLk6j1qUdT6FmxkMmNz

IT Consultancy Services

I'm now available for IT consultancy and software development services - Cloudee LTD.



Happy user of Digital Ocean (Affiliate link)


Version:master-619e08f203


Validate HTML 5