3.3. Disabling C-states by using a custom TuneD profile

Procedure

1. Display the active profile:

   # tuned-adm active
   Current active profile: network-latency

2. Create a directory for the custom TuneD profile:

   # mkdir /etc/tuned/network-latency-custom/

3. Create the /etc/tuned/network-latency-custom/tuned.conf file with the following content:

   [main]
   include=network-latency
   
   [cpu]
   force_latency=cstate.id:1|2

   This custom profile inherits all settings from the network-latency profile. The force_latency TuneD parameter specifies the latency in microseconds (µs). If the C-state latency is higher than the specified value, the idle driver in Red Hat Enterprise Linux prevents the CPU from moving to a higher C-state. With force_latency=cstate.id:1|2, TuneD first checks if the /sys/devices/system/cpu/cpu_<number>_/cpuidle/state_<cstate.id>_/ directory exists. In this case, TuneD reads the latency value from the latency file in this directory. If the directory does not exist, TuneD uses 2 microseconds as a fallback value.

4. Activate the network-latency-custom profile:

   # tuned-adm profile network-latency-custom