Re: acpi_idle: Very idle Core i7 machine never enters C3

[Pavel Machek]

On Tue 2010-01-26 02:47:40, Jeff Garrett wrote:
> Hi,
> 
> I was trying to chase down a theory that my desktop machine (a core i7)
> is running warm (the fan sounds like it's at full speed all the time,
> and I think it's not always acted this way -- hence the theory).
> 
> powertop is never showing it spending any time in C3...
> 
> I compiled a kernel without USB/sound/radeon, and ran without X.  I was
> able to get the wakeups/sec down below 20, but no time is spent in C3.

> This may be a complete red herring, but I added some printk logic to
> acpi_idle_bm_check(), and it is getting called often, but bm_status is
> always 1.  [I infer from this that the idle logic is trying to go into
> C3, but this check is stopping it...  Unless I misread something.]
> 
> Is this expected behavior or is this a legitimate problem?
> 
> How might I investigate this further?

DMA keeps system awake? Possibly USB?

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