SMP & CPU_SUSP_HLT

[RMH]

Hello gentlemen,

it seems CPU_SUSP_HLT does nothing for SMP kernels.

i386/i386/machdep.c:

#ifdef SMP
static int      cpu_idle_hlt = 0;
#else
static int      cpu_idle_hlt = 1;
#endif

It's noted that when enabled it will result in about 4.2%
loss in performance while doing buildworld. I haven't
checked with that, but I tested single-threaded applications
to suffer for about 2%, what shouldn't be a big difference.

Beyond power consumption, suspend on HLT may solve some
overheating issues common for multiprocessor systems. At
least, it does so in my case.

I suggest to remove #ifdef SMP, and place a warning into
NOTES. Let people decide.

---
Regards,
 Rhett


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