Meta's CRAM compresses memory in RAM for up to 452x speedup over ZRAM

A team led by Gregory Price at Meta has developed CRAM, a compression model that keeps compressed data in RAM instead of swap, unlike zswap and ZRAM. In read-only tests it delivered up to 452x the performance of ZRAM, dropping to 5.4x with 20% writes.

• CRAM uses a private NUMA node instead of pretending to be a block device
• Worst-case CRAM hits 489 million ops/sec versus 1.1 million for ZRAM
• With 20% writes the speedup falls to 5.4x due to folio migration
• Presented at Linux Plumbers Conference; memory accounting remains unsolved