Where did my cores go?

[mgnut57]

I have an atom-330 based system. This has 2 physical cores and with HT, it should show 4 logical cores.

I booted it with an Ubuntu live CD and see 4 cores, yes in my Gentoo system, it only shows 1 core.

Contents of /proc/config.gz are here: http://pastebin.com/DXtX0pYZ

As you can see, the SMP options are selected. This system used to show 4 cores under Gentoo, but an update (I don't know which), seems to have caused it to only see 1 core.

[roarinelk]

post dmesg output please (if possible include the working ubuntu one too)

[mgnut57]

[roarinelk]

unfortunately the interesting parts when the kernel starts are missing,
but apparently it only sees one core which it dutifully reports as up
(i.e. first line says "SMP alternatives: switching to UP code" meaning
it either only detected one core or something else is preventing it
from using SMP).

I also think you should enable these 2 .config options:
# CONFIG_NO_HZ is not set
# CONFIG_HIGH_RES_TIMERS is not set

and set CONFIG_LOG_BUF_SHIFT to 17 (currently 15), which
will let you get to the full dmesg.

Also, try 2.6.38.6 or better yet, latest -git sources.

[mgnut57]

[roarinelk]

the interesting parts of dmesg are still missing.
add "init=/bin/bash" to the kernel cmdline, save the dmesg to a file
(do a "mount -o rw,remount /" first), then boot the kernel normally again.

[mgnut57]

[doctork]

I notice you have ACPI disabled in your kernel command line. I'm betting that Ubuntu does not. Perhaps that's your problem. On my Atom D510, also dual core with HT, dmesg tells me

[roarinelk]

What doctork said.

Command line: root=/dev/sda2 pci=routeirq noapic irqpoll acpi=off

basically you should remove all but the "root" line.

[krinn]

smp cannot work without apic

[mgnut57]