Re: [Xen-devel] [PATCH] x86/watchdog: Use real timestamps for watchdog timeout

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 24/05/13 14:55, Tim Deegan wrote:
> At 13:48 +0100 on 24 May (1369403327), Andrew Cooper wrote:
>> On 24/05/13 13:41, Tim Deegan wrote:
>>> Of those two, I prefer (1), just because it doesn't add any cost to the
>>> normal users of NOW().
>> I was not planning to make any requirement to change users of NOW(). 
> Well, you were planning to make NOW() slightly more expensive by needing
> to look up which of the banekd alternatives is valid.  In any case, I
> think some sort of approximate version based on tsc will do.
>
> Tim.

I was planning to memcpy the shadow set over the main set as part of
calibration, leaving no alteration whatsoever to NOW().

An approximation from the TSC alone would be better so long as it is a
reasonable approximation.  I am concerned about how accuate a dumb
approximation would be for non-stable TSCs etc.

~Andrew

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