[sldev] AppendedAcks

Dale Mahalko dmahalko at gmail.com
Thu Apr 2 17:31:39 PDT 2009


On Thu, Apr 2, 2009 at 9:51 AM, Carlo Wood <carlo at alinoe.com> wrote:
> 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.
>

What you're seeing is discarding from the decompressed texture cache,
not from the on-disk texture cache.

There is a hidden texture cache in memory that never gets written to
disk, which contains raw RGB bitmaps of the JPEG2000 data. It is never
written to disk apparently for obfuscation purposes.


I have never delved deep enough to determine if this raw bitmap cache
is part of the 3D card's texture cache, or if it is an entire
duplication of the 3D VRAM cache.

So, you have the following hogging system memory with the client running:
- Operating system
- Client software
- VFS cache that is held fully in memory all the time
- Hidden decompressed raw bitmap texture cache of unknown size
- (possibly separate?) 3D card texture caching


When you teleport somewhere, it was previously reported by someone
here on SLDev that the decompressed raw-bitmap image cache is
completely dumped, and then the world must be completely
re-decompressed from the JPEG2000's on disk, which is extremely slow
and CPU intensive.

This is why the world appears gray anytime you teleport. It simply
threw all the previous decoded texture data away and starts redecoding
anew.

- Scalar Tardis / Dale Mahalko


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