The meaning of thermal throttle counters and package power limit notifications in Linux

Posted by Trustin Lee on Super User See other posts from Super User or by Trustin Lee
Published on 2012-08-09T02:54:15Z Indexed on 2012/10/05 15:41 UTC
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Whenever I do some performance testing on my Linux-installed MacBook Pro, I often see the following messages in dmesg:

Aug  8 09:29:31 infinity kernel: [79791.789404] CPU1: Package power limit notification (total events = 40365)
Aug  8 09:29:31 infinity kernel: [79791.789408] CPU3: Package power limit notification (total events = 40367)
Aug  8 09:29:31 infinity kernel: [79791.789411] CPU2: Package power limit notification (total events = 40453)
Aug  8 09:29:31 infinity kernel: [79791.789414] CPU0: Package power limit notification (total events = 40453)

I also see the throttle counters in the sysfs increases over time:

trustin@infinity:/sys/devices/system/cpu/cpu0/thermal_throttle
$ ls
core_power_limit_count  package_power_limit_count
core_throttle_count     package_throttle_count
$ cat core_power_limit_count 
0
$ cat core_throttle_count 
41912
$ cat package_power_limit_count 
67945
$ cat package_throttle_count 
67565

What do these counters mean?

Do they affect the performance of CPU or system? Do they result in increased deviation of performance numbers? (i.e. Do they prevent me from getting reliable performance numbers?)

If so, how do I avoid these messages and increasing counters? Would running the performance tests on a well-cooled desktop system help?

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