Re: [Bug #10710] [BISECTED] Lots of "rescheduling IPIs" in powertop

From: Andi Kleen
Date: Sun May 18 2008 - 16:30:44 EST

Thomas Gleixner wrote:

> stop these pointless ad hominem attacks!

Just my experience from past incidents sorry. I'm sure it never happened
to you.

>> [In case someone is interested it's CPUID 5 ECX bit 0 which enumerates
>> if the MWAIT enumeration is there. So the correct mwait_usable() that
>> would have avoided your problem would be something like (untested):
>> return c->cpuid_level >= 5 &&
>> ((cpuid_ecx(5) & 1) == 0 || (cpuid_edx(5) >> 4) & 0xf) > 0);
>> ]
> I'm interested, but I'd be even more interested in some useful pointer
> to the magic bitnumbers in that check, but don't exert yourself in
> providing the information,

It's documented in the IA32 SDM vol2 as part of the CPUID description.
It's a reasonable expection that everyone hacking on cpuid code has that
at hand.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at