[mnutt]

There are workloads that will saturate a redis instance's CPU: using it as an LRU cache, eventually you will hit the configured memory limits and adding new keys will require finding old keys to delete. Eventually it may also require redis to do memory defragmentation which can be fairly intensive.

[tomnipotent]

> There are workloads that will saturate a redis instance's CPU

I might imagine this scenario if you're excessively using smembers and a few other slow ops, but I have yet to see CPU issues outside of bad eval's.

> require finding old keys to delete

LRU/LFU eviction is not particularly CPU intensive.

> redis to do memory defragmentation which can be fairly intensive

Active defrag has relatively negligible overhead, and assuming jemalloc even more so.

[mnutt]

Nothing but lots of small (~100b) pipelined SETs and a small number of GETs here and there. Only 10MB/s but at 100k SETs/sec redis’s CPU core sits at 60-70%. Active defrag can easily send it into a death spiral.