Memory compression? I can't find any good resources to read about it, any hints?...

kccqzy · on Nov 10, 2022

It doesn't destroy performance for the simple reason that nowadays memory access is slower than pure compute. If you need to use compute to produce some data to be stored in memory, your overall throughput could very well be faster than without compression.

There have been a large amount of innovation on fast compression and fast decompression in recent years. Traditional compression tools like gzip or xz are geared towards higher compression ratio, but memory compression tends to favor speed. Check out those algorithms:

* lz4: https://lz4.github.io/lz4/

* Google's snappy: https://github.com/google/snappy

* Facebook's zstd in fast mode: http://facebook.github.io/zstd/#benchmarks

miohtama · on Nov 10, 2022

On Mac, you can find Compressed memory in Activity monitor.

It’s something similar to swap - apps do not need to have built in support for it.

flatiron · on Nov 10, 2022

It segments a certain amount of ram to “swap” to which means compress and store. Normal blue sky ram operations are not compressed on macOS

smcleod · on Nov 10, 2022

Many operations are actually a lot faster with compressed memory than without. It's all about where the bottleneck is.

comboy · on Nov 10, 2022

Oh, yes compressed swap makes much more sense, thanks.

kergonath · on Nov 10, 2022

It is not compressed swap, the compressed data is still in RAM. The OS just compresses inactive memory, with a couple of criteria to define “inactive”.