CPU Power Management Troubleshooting
- ===== Q: CPUPM should be supported, but the CPUs are always running at the fastest speed. What's going on?
- Answer 1: There is an issue in Nevada builds 110 and newer where on some systems, a relatively small amount of system background activity can result in CPUPM too aggressively running the CPUs at the fastest speed. A fix integrated into build 117 to help address this (6818514) (so upgrading will likely help), although on some systems with enough background activity this can still be seen. The complete fix should be integrated shortly, but in the meanwhile, you can work around the issue by changing this line in /etc/power.conf (and then running pmconfig(1m)):
From:
cpupm enable
To:
cpupm enable poll-mode
- Answer 2: Use powertop to verify that your system is indeed stuck running at the fastest speed. Also take a look at the "C-states" in the left hand column. This indicates what percentage of time the CPU is spending running (in the C0 state), vs. Idle and power managed (C1, C2, ...). If there is a significant amount of time spent in C0 (say, 20% or more), use something like prstat(1m) to see what is running and keeping the system busy.
on 2009/10/26 12:10