[Opensim-dev] Bit packing

[Melanie]

Hi,

the point is that the Linden protocol uses it in places.

Using acscessor functions that retrieve individual values forces a 
memory operation where register operation would do the job.

I suppose that particular case is a minor performance concern, but it 
does highlight what I consider to be serious shortcomings of the model.

I am totally unconvinced of the need to even do any work on this at all. 
The Packet and it's friends are not the issue, and I don't think they 
ever were.
I have fixed so much bottlenecking in the stack already, and it's shown 
me that the issues are not in the packet class. I don't know if that is 
part of a crusade to remove libsl/omv, but if so, it's not declared as such.

Melanie


Mana Janus wrote:
> Melanie,
> 
> Not sure, if I understand correctly what you mean...
> 
>> Not really. Two memory accesses to retrieve 2 values packed into one 
>> byte are 2 accesses. in C#, C++, unsafe blocks or even assembly. 
>> They remain inefficient.
>>   
> 
> The alternative seems to store the 2 values in 2 bytes? How would two 
> memory accesses to retrieve two values from two bytes be more efficient 
> than retrieving them from the same byte? And if they are stored in the 
> same byte you have always the option to retrieve both with only one 
> memory access.
> 
> Don't get me wrong, I don't want to advertise bit packing, just would 
> like to understand your argument...
> 
> Mana
> 
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