Re: [PATCH] amd76x_pm on 2.6.0-test9 cleanup

From: Charles Lepple
Date: Tue Nov 04 2003 - 15:53:12 EST

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

* Charles Lepple <clepple@xxxxxx> [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?

At HZ=200, it would take a while to notice. I used adjtimexconfig, which counts the number of kernel ticks which occur in 70 seconds (according to the RTC). The RTC is pretty stable without power management, so I tend to trust it. I think I ended up with a value of tick=11000 (compensation for a 10% slow clock), and if I left the machine idle, ntpd would converge based on the new tick value.

Then again, I don't think I tried HZ>=200 on -test9. (When I got Pasi's -test9 patch, I applied it to a -test8-bk kernel with HZ=1000-- I don't remember exactly which one.) Based on his followup email, timekeeping may be better in -test9. I'll check.

I've been using kexec for reboots recently though as the bios reboot is soo slow.

The slowness on my system is supposedly related to ECC initialization, but it's only ~30 seconds for 512MB. Still, if I upgrade the memory, that's a good tip.

But just to verify: 2.6.0-test9 & amd76x_pm as module, and the system drops
into sleep mode when the module is loaded for the first time until power is
pressed? And this does not happen after cold reboots or when the amd76x_pm
is reloaded?


Charles Lepple

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