linux-kernel - Re: x86_64 dynticks not working prev: cpuidle, dynticks compatible or no?

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Date:	Fri, 07 Dec 2007 21:50:36 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Ed Sweetman <safemode2@...cast.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: x86_64 dynticks not working   prev: cpuidle,
 dynticks compatible or no?

Ed Sweetman wrote:
> System is idle now, previously it was doing something i couldn't halt at 
> the time.  I'm looking at "Local timer interrupts" in the "Loc:" section 
> of /proc/interrupts.
> Across 1 second while the system is pretty much idle, i still get 300 
> interrupts. My HZ variable is set to 300 in the kernel config, so this 
> is expected but I was under the assumption that dynticks/tickless being 
> compiled in would cause that to be much lower.
> 
> Am I reading the wrong section of /proc/interrupts  to verify if 
> dynticks is working or not? Again, i see no difference in cpu temp at all.

Try running powertop ( http://www.lesswatts.org/projects/powertop/ ) and 
see what it reports.

I don't think dynticks will generally save huge amounts of power on a 
typical desktop machine. The big gains come from being able to stay in 
deep sleep C-states (C2/C3) for longer periods of time, but most desktop 
machines only enable sleep states down to C1.

> 
> In case it helps, this is an athlon64 x2 with apic functioning and both 
> cores active in 64bit mode. dmesg is below.
> not related :
> Some additional notes:  it87 is my lm_sensor, it doesn't work in this 
> kernel, yet it did in 2.6.22.  Perhaps enabling high precision timers 
> changed something in acpi land.
> 
> I enabled tcp dma offloading in this kernel, i get debugging output 
> related to it, error is at the last line.  No corruption or otherwise 
> bad behavior.   Transferring via cifs at 9.7MB/sec "incoming" took about 
> 15% of one cpu...  I never bothered to check if that is the norm but i 
> suspect i'll be removing that feature as it seems to not play nice with 
> the kernel.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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