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

[Dave Winchell <dwinchell@virtualiron.com>]

Keir Fraser wrote:

>On 5/3/08 17:25, "Dave Winchell" <dwinchell@virtualiron.com> wrote:
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>>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.
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I see the one shot messages on 64 bit and no complaints at all on 4u432 
Linux.
And I have been ignoring them.

> -- Keir
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