Valkey 9.2 forkless BGSAVE cuts memory spike from 350MB to 10MB

Valkey 9.2.0-rc1 adds a forkless BGSAVE mode: on a 1.1GB dataset under sustained writes, the memory spike dropped from ~355MB to ~10MB. The trade-off is slower saves (5–6s vs 3s) and about 15% lower write throughput. The option can only be set at server startup and does not affect AOF rewrites.

• BGSAVE memory spike: 354.7MB with fork vs 0MB COW and 9.9MB cgroup without fork
• Save wall time rose from 3s to 5–6s on the same dataset
• Write throughput fell from 27,202 to 23,034 ops/sec (−15%)
• forkless-infrastructure-enabled is startup-only; AOF rewrites still fork