9.1 callout behavior

[Alexander Motin]

On 04.12.2013 14:49, Bret Ketchum wrote:
>      See attached. I've tightened up the definition of inconsistent
> callout calls. A "Whoops" message indicates the callout function was
> called either side of a 10ms window than what was expected. "Ouch"
> indicates the cyclecounter does not agree with the expected period given
> the same 10ms fudge factor.

I have this module running on two of my tests systems with stable/9 
(2xE5645 and i7-3770) and half hour later I see no any of related 
messages on consoles. Could you share what exactly do you have there logged?

> On Wed, Nov 27, 2013 at 3:28 AM, Bret Ketchum <bcketchum at gmail.com
> <mailto:bcketchum at gmail.com>> wrote:
>
>     Alexander,
>
>          In this scenario, global ticks should have increased by 100
>     every interval. When the wheels go off the truck, global ticks will
>     be 800+ yet only a fraction of usual number of clock cycles have
>     increased.
>
>          I'll try to cook up an kernel module which will reproduce.
>
>
>     On Wed, Nov 27, 2013 at 1:42 AM, Alexander Motin <mav at freebsd.org
>     <mailto:mav at freebsd.org>> wrote:
>
>         Hi, Brett,
>
>         Could you tell more about "ticks has increased 8x"? Tickless
>         mode it is somewhat tricky algorithm to track global ticks
>         counter, but it should not jump that big. Jumps there could
>         easily trigger wrong callout behavior in 9 (in 10 callout code
>         was rewritten and no longer depend on ticks).
>
>
>         On 21.11.2013 22:19, Adrian Chadd wrote:
>
>             It sounds like you may have found an interesting test case.
>
>             Mav, any ideas?
>
>             On 21 November 2013 05:20, Bret Ketchum <bcketchum at gmail.com
>             <mailto:bcketchum at gmail.com>> wrote:
>
>                        I've a callout which runs every 100ms and does a
>                 bit of accounting
>                 using the global ticks variable. This one-shot callout
>                 was called fairly
>                 consistently in 8.1, every 100ms give or take a few
>                 thousand clocks. I've
>                 recently upgraded to 9.1 and for the most part the
>                 period is consistent.
>                 However, periodically the callout function is executed
>                 anywhere between 5ms
>                 to 20ms after the callout was reset and the function
>                 returned while global
>                 ticks has increased 8x. The hardware has not changed
>                 (using the same
>                 timecounter configuration):
>
>                 CPU: Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz
>                 (2500.05-MHz K8-class CPU)
>
>                 kern.timecounter.hardware: TSC-low
>                 kern.timecounter.tick: 1
>                 kern.timecounter.invariant___tsc: 1
>                 kern.timecounter.smp_tsc: 1
>
>                        And default eventtimer configuration:
>
>                 kern.eventtimer.singlemul: 2
>                 kern.eventtimer.idletick: 0
>                 kern.eventtimer.activetick: 1
>                 kern.eventtimer.timer: LAPIC
>                 kern.eventtimer.periodic: 0
>
>                       If tickless mode is disabled the inconsistency
>                 goes away. Is the
>                 premature expiration of the callout expected? Is the
>                 jump in global ticks
>                 typical (say from 100 ticks to 800 ticks in 1.5ms)?
>
>                       Bret
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>
>
>         --
>         Alexander Motin
>
>
>


-- 
Alexander Motin