idle process keeping cpu 150% busy in freebsd 9.1-amd64

[John Baldwin]

On Thursday, May 30, 2013 4:29:07 pm Kostas Oikonomou wrote:
>    Hello,
>    I am new to FreeBSD. I just installed 9.1-RELEASE-p3 (comes with PC-BSD
>    9.1) on an HP Pavilion s5100z.  The machine has a dual-core AMD Athlon
>    7750 processor.
>    What happens is that when I am doing nothing on the machine, one core
>    is about 150%
>    busy running the idle process:
>    USER        PID  %CPU %MEM    VSZ   RSS TT  STAT STARTED    TIME
>    COMMAND
>    root         11 152.9  0.0      0    32 ??  RL    8:19AM 2:14.50 [idle]
>    root          0   0.0  0.1      0  2672 ??  DLs   8:19AM 0:00.36
>    [kernel]
>    root          1   0.0  0.0   6276   416 ??  SLs   8:19AM 0:00.05
>    /sbin/init --
>    I have read [1]http://forums.freebsd.org/showthread.php?t=38757, which
>    seems to be relevant, and I tried
>    sysctl -w kern.eventtimer.timer=<various choices>
>    as they suggest, but to no avail.
>    The same problem also on my Dell E6510 laptop, which has an Intel Core
>    i7:  the idle process is making one core run at about 400%.
>    Any help would be greatly appreciated.
>                                Kostas

This is normal.  The idle process has a thread per-CPU that the scheduler runs 
when the CPU is idle.  Even if the CPU is actually asleep in a Cx state, the 
time it is asleep is accounted to the idle thread.

I added a 'Z' flag to hide the idle threads in top (they are especially
noisy on an idle machine with a lot of CPUs if you use top -SH).

-- 
John Baldwin