cbloom rants: How Oodle Kraken and Oodle Texture supercharge the IO system of the Sony PS5

Sony has previously published that the SSD is capable of 5.5 GB/s and expected decompressed bandwidth around 8-9 GB/s, based on measurements of average compression ratios of games around 1.5 to 1. While Kraken is an excellent generic compressor, it struggled to find usable patterns on a crucial type of content : GPU textures, which make up a large fraction of game content. Since then we've made huge progress on improving the compression ratio of GPU textures, with Oodle Texture which encodes them such that subsequent Kraken compression can find patterns it can exploit. The result is that we expect the average compression ratio of games to be much better in the future, closer to 2 to 1.

Oodle Kraken is the lossless data compression we invented at RAD Game Tools, which gets very high compression ratios and is also very fast to decode. Kraken is uniquely well suited to compress game content and keep up with the speed requirements of the fast SSD without ever being the bottleneck. We originally developed Oodle Kraken as software for modern CPUs. In Kraken our goal was to reformulate traditional dictionary compression to maximize instruction level parallelism in the CPU with lots independent work running at all times, and a minimum of serial dependencies and branches. Adapting it for hardware was a new challenge, but it turned out that the design decisions we had made to make Kraken great on modern CPUs were also exactly what was needed to be good in hardware.

The Kraken decoder acts as an effective speed multiplier for data loading. Data is stored compressed on the SSD and decoded transparently at load time on PS5. What the game sees is the rate that it receives decompressed data, which is equal to the SSD speed multiplied by the compression ratio.

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