it seems to me that there are 2 ways that compression could give speed benefits. here by compressing pages in RAM we can fit more in it, and so avoid costly fall backs to using slow disk. This will give a huge speed up on setups where you hit swap often, or where you benefit from having files in the RAM cache.
But compression can also (in some cases) give you speedups by increasing bandwidth. For example if i my hard disk can manage 100MB/s, and i enable the compression option in my filesystem, then i might be able to get 200MB/s of data out of it (assuming an average 0.5 compression ratio). This works when the interface is slower than (de)compression.
So i wonder if there is any opportunity that compression could help get around the problem of limited memory bandwidth. If memory bandwidths are of the order 10s of GB/s, shared between multiple CPUs, can the CPU decode fast enough for this to be any use? or is latency to RAM more of an issue than bandwidth?