On 11 Mar 2011, at 17:03, Andrew Deason <[email protected]> wrote:

> On Fri, 11 Mar 2011 15:01:44 +0000
> Simon Wilkinson <[email protected]> wrote:
> 
>> However, I'm less sure about the time resolution variable. This means  
>> that we are in effect tripling the size of every time payload in AFS.  
>> I'd be interested in a far more detailed discussion of the pros and  
>> cons for including this variable. In particular, will this information  
>> really change sufficiently rapidly that it needs to be included with  
>> every single piece of time data? Does it give us benefits that  
>> specifying a per-service granularity using capability bits won't?
> 
> No, I don't think that is sufficient. A service can support
> 100ns-granular time, but say it reads a time value from disk from a
> structure that represents time in seconds.

In what circumstances would you be comparing this value with one derived from a 
source with higher granularity, though? I'm really interested in specific use 
cases here. We're talking about adding a significant overhead here - I think we 
need to clearly understand the benefits.

> If you transmit that time (or
> a time derived from it), it is inferred from the other side that it has
> 100ns granularity if this is done just with a per-service cap bit, which
> is incorrect.

You could easily require that an implementation that advertises a specific 
level of granularity provides that for all values (and rounds down items that 
come from higher granularity sources)

S.
> 

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