Multicore laptops and turning off CPU cores

[Artem Kachitchkine]

> This is Linux specific, but we can add Solaris and *BSD support easily.
> Artem, Joe, what are the commands?

I don't know much about it, I think in Solaris it comes down to virtual vs 
physical CPU:

# psrinfo -vp
The physical processor has 32 virtual processors (0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
30, 31)
   UltraSPARC-T1 (cpuid 0 clock 1000 MHz)

or

# psrinfo -vp
The physical processor has 2 virtual processors (0 2)
   x86 (GenuineIntel family 15 model 2 step 5 clock 3190 MHz)
         Intel(r) Xeon(tm) CPU 3.20GHz
The physical processor has 2 virtual processors (1 3)
   x86 (GenuineIntel family 15 model 2 step 5 clock 3190 MHz)
         Intel(r) Xeon(tm) CPU 3.20GHz

You can offline the CPUs with psradm:

# psrinfo
0       on-line   since 08/16/2006 11:58:09
1       on-line   since 08/16/2006 11:58:17
2       on-line   since 08/16/2006 11:58:19
3       on-line   since 08/16/2006 11:58:21
# psradm -f 0
# psrinfo
0       off-line  since 08/17/2006 10:51:49
1       on-line   since 08/16/2006 11:58:17
2       on-line   since 08/16/2006 11:58:19
3       on-line   since 08/16/2006 11:58:21

But I don't know how exactly that corresponds to CPU power management. I think 
the kernel will do the right thing when a CPU is offlined.

-Artem.