Problem with HT support in 5.4

[Dmitry Mityugov]

On 5/27/05, Jacob S  wrote:
> Hello list,
> 
> I upgraded a few 5.3 servers to 5.4 yesterday and everything seemed to
> go well. After booting the new kernel, dmesg correctly showed 2 logical
> cpus (1 xeon with HT).
> 
> However, when I look at top's output, it always shows at least 50% cpu
> idle time - even when the load is above 10. To confirm this, I ran
> burnP6 from the cpuburn port - even with over a hundred apache processes
> going, exim running and a few other things, top still reported the cpu
> as 50% idle. The 'C' column in top, between 'State' and 'Time' also
> shows everything as being run on cpu 0.
> 
> `ps ax | grep cpu` reports this:
>  11  ??  RL     0:00.00 [idle: cpu1]
>  12  ??  RL   931:45.24 [idle: cpu0]
> 108  ??  DL     0:04.02 [schedcpu]
> 
> So it looks like smp support is enabled and it sees the HT enabled
> processor, but it's not using the second logical cpu. Is there something
> I missed in compiling the kernel, or is this a bug? I have confirmed it
> on two 5.4 servers now.

Was option smp used to compile the kernel? What other changes to the
kernel configuration file were made?

Dmitry