[Tinyos-host-mote-wg] [Tinyos-2.0wg] NSDI submission

[Philip Levis]

Attached.

I think the key results people in the WG probably care about are  
tables 4-7. Basic takeaways:

Table 4: Cory's Timer library is a good thing.
Table 5: 2.x subsystems lead applications to use 20-50% more program  
memory (20-50%)[1] and between 25-40% less RAM.
Table 6: Programs use ~25% fewer CPU cycles, with one exception[1].
Table 7: The 2.x CC2420 stack can communicate up to 150% faster than  
1.x.

[1] The extra code comes from the timer system (300 bytes), scheduler  
(needs task pruning optimization), the better RNG (1K), and the  
serial stack. The one app where 2.x uses more CPU cycles than 1.x is  
due to the serial stack.

Based on these results, a few observations:

1) Given the directions Joe is arguing for (seems like supporting  
tiny MSP430s as well as big MSP430s), the decision to allow a  
platform or app to replace the RNG was a good one. This also allows  
eliding the 32-bit libraries if needed.

2) A more thorough analysis of the gains of task pruning could push  
it to be a requirement or relegate it to unnecessary. Cory had some  
good initial data, which is a great place to start. One issue here is  
that we want to look at some reasonable apps.

3) The serial stack needs a good code review/profiling/refactoring.  
Ben and I threw together something that we thought was nice and  
flexible, but it is a bit bloated. The CPU cycles don't bother me  
nearly as much as the code cost.

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Phil
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