Re: (progress on hpet accuracy) and Re: [Xen-devel] [PATCH] Add a timer mode that disables pending missed ticks

[Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>]

Keir Fraser wrote:

> On 5/3/08 17:25, "Dave Winchell" <dwinchell@xxxxxxxxxxxxxxx> wrote:
>
>  
>
> > In 2.6.9, it looks like cur_timer->mark_offset() call from
> > timer_interrupt in
> > 32 bit arch/i386/kernel/time.c invokes, for hpet, mark_offset_hpet(),
> > which computes
> > missed ticks based on hpet counter. mark_offset_pit() does nothing.
> > mark_offset_tsc() does compute missed ticks.
> >
> > In 64 bit 2.6.9, the timer_interrupt() in arch/x86_64/time.c does hpet
> > reads directly HPET_T0_CMP, HPET_COUNTER to calculate missed ticks.
> >
> > So from the code perspective, it looks like missed ticks are computed
> > for 32
> > and 64 bit Linux using hpet clocksource.
> >    
> Ah. I looked at 2.6.18 which seems to have neither the mark_offset nor the
> GENERIC_TIME approach in its arch/i386 time code. But yeah, it does look
> like in general Linux 2.6 is robust to missed ticks when using hpet. That's
> good.
>
> Do you see and simply ignore warning messages from 64-bit Linux when using
> hpet (or otherwise not doing missed-tick handling in Xen), by the way? I
> know 64-bit Linux is keen to warn about missed ticks, although it does look
> like at least the warning is one shot.
>  
I see the one shot messages on 64 bit and no complaints at all on 4u432 
Linux.
And I have been ignoring them.

> -- Keir
>
>
>  

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel