kern/108954: [acpi] 'sleep(1)' sleeps > 1 seconds when speedstep (Cx) is in economy mode

[John Baldwin]

The following reply was made to PR kern/108954; it has been noted by GNATS.

From: John Baldwin <jhb at FreeBSD.org>
To: bug-followup at freebsd.org,
 huntting at hunkular.glarp.com
Cc:  
Subject: Re: kern/108954: [acpi] 'sleep(1)' sleeps &gt;1 seconds when speedstep (Cx) is in economy mode
Date: Tue, 15 Jan 2008 10:18:30 -0500

 The problem as Bruce indicated is that some CPUs turn off the lapic timer
 when entering C3 so the CPU stays asleep until the next device interrupt.
 Your CPU isn't any slower during C3 though.  That is a separate facility.
 You can try using C2 to see if that works ok as it may not power off your
 lapic timer.
 
 One possible fix (but a bit of work) would be to schedule one of the HPET
 comparators to fire the next lapic timer interrupt before going into C3.
 Even better is to stop doing periodic interrupts altogether and instead
 doing deadline interrupts via the HPET but that is a much larger piece of
 work.
 
 Also, more recent 6.x should work fine with suspend/resume with 'device apic'
 for the non-SMP case now.
 
 -- 
 John Baldwin