Re: [PATCH] amd76x_pm on 2.6.0-test9 cleanup

From: Charles Lepple <clepple@ghz.cc>
To: Tony Lindgren <tony@atomide.com>
Cc: psavo@iki.fi, lkml <linux-kernel@vger.kernel.org>,
	john stultz <johnstul@us.ibm.com>
Subject: Re: [PATCH] amd76x_pm on 2.6.0-test9 cleanup
Date: Tue, 4 Nov 2003 17:38:33 -0500	[thread overview]
Message-ID: <9F0055D6-0F17-11D8-A943-003065DC6B50@ghz.cc> (raw)
In-Reply-To: <20031104200517.GD1042@atomide.com>

On Tuesday, November 4, 2003, at 03:05 PM, Tony Lindgren wrote:

> * Charles Lepple <clepple@ghz.cc> [031104 11:45]:
>> On Tuesday 04 November 2003 02:15 pm, Tony Lindgren wrote:
>>> I've heard of timing problems if it's compiled in, but supposedly 
>>> they
>>> don't happen when loaded as module.
>>
>> In some of the earlier testX versions of the kernel, I did not see any
>> difference between compiling as a module, and compiling into the 
>> kernel. (It
>> is currently a module on my system.)
>>
>> I did, however, manage to keep ntpd happy by reducing HZ to 100. Even 
>> raising
>> HZ to 200 is enough to throw off its PLL. The machine is idle for 90% 
>> of the
>> day, though, so I don't know if the PLL is adapting to the fact that 
>> the
>> system is idling, but the values for tick look reasonable.
>
> Interesting, sounds like the idling causes missed timer interrupts? 
> Can you
> briefly describe what's the easiest way to reproduce the timer 
> problem, just
> change HZ to 200 and look at the system time?

Weird. On -test9-bk at HZ=1000, with amd76x_pm loaded as a module 
(lazy_idle=800, the default), the system clock is running fast.

With ntpd running, the clock was stepped back 2.5 seconds twice in 20 
minutes.

Here's what I get from adjtimexconfig (after stopping ntpd, of course):

# adjtimexconfig
Comparing clocks (this will take 70 sec)... adjusting system time by  
-126.211  sec/day
Done

Now tick is 9985. I distinctly remember it being somewhat over 10,000 
the last time I ran with HZ=1000 and amd_76x_pm active. With HZ=100, 
adjtimexconfig sets tick=10002.

I'm not entirely sure what the "acpi" interrupt is doing-- it 
increments about once every two seconds when the system is idle, and 
various types of system activity make it happen more frequently. At 
least I'm not getting any "irq 9: nobody cared!" messages anymore (the 
button module is loaded, so I guess it is handling it). If I don't have 
amd76x_pm loaded, the acpi interrupt is triggered a couple of times 
after button is loaded, but then it doesn't happen again until I 
actually press a button.

-- 
Charles Lepple
ghz.cc! clepple