Re: [PATCH] Dynamic tick, version 050127-1

[Pavel Machek]

Hi!

> > > > > > I used your config advices from second mail, still it does not work as
> > > > > > expected: system gets "too sleepy". Like it takes a nap during boot
> > > > > > after "dyn-tick: Maximum ticks to skip limited to 1339", and key is
> > > > > > needed to make it continue boot. Then cursor stops blinking and
> > > > > > machine is hung at random intervals during use, key is enough to awake
> > > > > > it.
> > > > > 
> > > > > Hmmm, that sounds like the local APIC does not wake up the PIT
> > > > > interrupt properly after sleep. Hitting the keys causes the timer
> > > > > interrupt to get called, and that explains why it keeps running. But
> > > > > the timer ticks are not happening as they should for some reason.
> > > > > This should not happen (tm)...
> > > > 
> > > > :-). Any ideas how to debug it? Previous version of patch seemed to work better...
> > > 
> > > I don't think it's HPET timer, or CONFIG_SMP. It also looks like your
> > > local APIC timer is working.
> > 
> > I turned off CONFIG_PREEMPT, but nothing changed :-(.
> 
> What about reprogramming the timers in time.c after the sleep? Do
> you to dyn_tick->skip = 1; part in dyn_tick_timer_interrupt?

Yes, when I enabled debugging, dbg_dyn_tick_irq() was reached and
produced lot of noise to syslog. After I done nothing for a while,
machine would just sit there and wait, not doing anything. When it was
hung, dbg_dyn_timer_tick was not reached.

> It could also be that the reprogamming of PIT timer does not work on
> your machine. I chopped off the udelays there... Can you try
> something like this:

I added the udelays, but behaviour did not change.

> --- a/arch/i386/kernel/time.c	2005-01-27 12:58:04 -08:00
> +++ b/arch/i368/kernel/time.c	2005-02-02 19:01:31 -08:00
> @@ -479,8 +480,11 @@
>  
>  	spin_lock_irqsave(&i8253_lock, flags);
>  	outb_p(0x34, PIT_MODE);		/* binary, mode 2, LSB/MSB, ch 0 */
> +	udelay(10);
>  	outb_p(skip & 0xff, PIT_CH0);	/* LSB */
> +	udelay(10);
>  	outb(skip >> 8, PIT_CH0);	/* MSB */
> +	udelay(10);
>  	spin_unlock_irqrestore(&i8253_lock, flags);
>  }
>  
								Pavel
-- 
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