Caveats of rebuilding the kernel on FreeBSD AMD64

I my previous post I talked about rebuilding the kernel on a AMD64 machine with dual processors, what I didn't know at the time is the default installed kernel enables SMP but the GENERIC kernel profile does not. Enabling SMP in the FreeBSD kernel is quite easy all thats necessary is to add the SMP option prior to rebuilding the kernel.

options         SMP                     # Enable SMP kernel

Once this is done just follow the same steps I have described in previous posts. After you have completed the kernel install you can verify that the operating system sees all the processors by running one of the following commands.

[root@test] [/root]> cat /var/log/messages | grep cpu
Jan 30 10:33:11 test kernel: cpu0: <ACPI CPU> on acpi0
Jan 31 07:48:42 test kernel: cpu0 (BSP): APIC ID:  0
Jan 31 07:48:42 test kernel: cpu1 (AP): APIC ID:  1
Jan 31 07:48:42 test kernel: cpu0: <ACPI CPU> on acpi0
Jan 31 07:48:42 test kernel: cpu1: <ACPI CPU> on acpi0

[root@test] [/root]> ps -aux | grep cpu
root      10 99.0  0.0     0    16  ??  RL    7:48AM 783:07.85 [idle: cpu1]
root      11 99.0  0.0     0    16  ??  RL    7:48AM 781:42.93 [idle: cpu0]
root      42  0.0  0.0     0    16  ??  DL    7:48AM   0:00.60 [schedcpu]
kkikta 16847  0.0  0.1  5920  1256  p0  S+    8:52PM   0:00.00 grep cpu

[root@test] [/root]> top -n
last pid: 16900;  load averages:  0.00,  0.00,  0.00  up 0+13:05:43    20:53:44
27 processes:  1 running, 26 sleeping

Mem: 12M Active, 13M Inact, 31M Wired, 20M Buf, 1912M Free
Swap: 512M Total, 512M Free


  PID USERNAME  THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
  635 pgsql       1   8    0 53580K  5776K nanslp 0   0:02  0.00% postgres
  624 pgsql       1  96    0 53580K  5480K select 1   0:02  0.00% postgres

As you probably noticed I colored the text in red that distinguishes between processors.