On 2017-03-02 10:08, Timothy Arceri wrote:
On 02/03/17 18:45, Tobias Droste wrote:
Hi Timothy,
if you plan to support multiple compression algorithms, shouldn't
"struct
cache_entry_file_data" contain some info about what compression
algorithm was
used to compress the data? Or is this already there and I missed it?
I don't plan to support more than one. I'm just saying it's a
possibility for the future, depending on further analysis and
requirements from different hardware. But right now I would just like
to land zlib support so we have a baseline to work from.
Like outlined on IRC, for the time being can you reconsider the
compression level, though?
The cache currently quite noticeably affects shader loading time on
first hit, i.e. when the cache is cold. Cache I/O and compression is
right now done synchronously, so it even happens without compression on
a system with fast SSD. Here's a summary of the numbers I gathered from
the initial loading screens of DE:MD on an Athlon X4 860k:
No Cache 215 sec
Cold Cache zlib BEST_COMPRESSION 285 sec
Warm Cache zlib BEST_COMPRESSION 33 sec
Cold Cache zlib BEST_SPEED 264 sec
Warm Cache zlib BEST_SPEED 33 sec
Cold Cache no compression 266 sec
Warm Cache no compression 34 sec
The total cache size for that game is 48 MiB with BEST_COMPRESSION, 56
MiB with BEST_SPEED and 170 MiB with no compression.
What In conclude from these numbers is that
a) the cache works really well! A warmed cache cuts down loading time by
an order of magnitude,
b) compression does a good job of reducing the cache size (which
probably helps with traditional spinning disk HDDs, and when disk space
is limited),
c) decompression always seems Fast Enough On My Computer™.
However, I also notice that BEST_COMPRESSION doesn't really affect the
total size of the cache files much compared to BEST_SPEED, while it does
noticeably increase the cold cache shader loading time. So in the end,
BEST_SPEED might be a better compromise, particularly for systems with a
slow CPU.
Apart from that, consider the series
Reviewed-by: Grigori Goronzy <g...@chown.ath.cx>
Best regards
Grigori
Am Donnerstag, 2. März 2017, 03:20:05 CET schrieb Matt Turner:
On Wed, Mar 1, 2017 at 2:19 PM, Timothy Arceri
<tarc...@itsqueeze.com>
wrote:
IMO we should go with zlib and people can provide future patches
with
justifications/stats for using a different library over zlib just
like we
do for any other performance based patch.
Yes, agreed. "Which compression should we use?" is one of the easiest
bikesheds to paint.
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