[sldev] Texture caching [was: AppendedAcks]

[Philippe Bossut (Merov Linden)]

Hi guys,

Improving the texture cache performance is one of the things we want  
to get right in this new http-texture branch. There has been quite a  
bit of discussion on this and we haven't forgotten it (see http://wiki.secondlife.com/wiki/Talk:Texture_Cache) 
. There are a couple of changes being merged right now (CG working on  
it as I type) in the branch that are related to this. May be steve  
will tell us more about it (I don't want to say something stupid here  
before I have a chance to experiment with the new code myself).

Anyway, yes, the discard algorithm has issues, the LRU is not  
adequate, we need cataloging of textures and these are all things we  
will be working on in the http-texture branch. Again, a massive change  
and a reason why we need to make that in the open.

Cheers,
- Merov

On Apr 2, 2009, at 10:27 AM, Tateru Nino wrote:
> Carlo Wood wrote:
>>
>> On Wed, Apr 01, 2009 at 03:15:14PM -0700, Philip Rosedale wrote:
>>
>>> I have a special place in my heart, though, for anyone who spots a  
>>> case where
>>> we are inefficiently sending data.  We need every byte we can get,  
>>> both in
>>> terms of latency and total bandwidth implications.  One project  
>>> I'd love to get
>>> to (and perhaps have community help with) is a careful examination  
>>> of all
>>> existing messages to look for bytes we could save.
>>>
>> Hey - well, I know an obvious case where we can save lots
>> and lots of bandwidth:
>>
>> Stop re-sending the same textures over and over again.
>>
>> I'm sure I have my cache not a single byte smaller than most
>> people (I have the slider all the way to the max, 1 GB), but
>> everytime I go to a new sim and then return home, everything
>> is gray and apparently has to be re-downloaded.
>>
>> I frequent maybe 10 or so sims a lot - some more than
>> others. And the textures that are in those sims have to
>> be downloaded, again and again and again.
> Concur. The discard algorithm seems to be *far* too agressive, and  
> this issue keeps coming up over and over. From monitoring the  
> viewer's activity, there are textures that get downloaded absurd  
> numbers of times, and many times within comparatively short periods  
> of time.
>
> Add another level of hash-buckets to the directory store, if there  
> are performance issues in dealing with a single directory full of  
> files, but the goal is to keep the content transfers to a minimum to  
> accomplish the job, right? Saves bandwidth for all, and should  
> reduce the impact on the grid.