Tune Redis Memory
Set maxmemory = 75 % of server RAM and maxmemory-policy = allkeys-lru (or volatile-lru if you rely on TTLs). Watch used_memory_rss / used_memory in INFO — a ratio > 1.5 = fragmentation, run MEMORY PURGE. MEMORY USAGE
Below: details, example, related terms, FAQ.
Details
- maxmemory-policy: allkeys-lru (default for cache), volatile-lru (mixed cache+store)
- MEMORY DOCTOR gives recommendations straight from Redis
- Fragmentation: jemalloc usually copes, but after a mass DEL it can hit 2×
- redis-cli --bigkeys scans and lists top keys by size
- Active defragmentation: activedefrag yes in config
Example
# Quick memory audit
$ redis-cli --bigkeys
# top-10 keys by size
$ redis-cli --memkeys --memkeys-samples 100
# Check one key
$ redis-cli MEMORY USAGE sessions:user:1234
(integer) 2048
# Rebalance/defrag
$ redis-cli CONFIG SET activedefrag yes
$ redis-cli MEMORY PURGERelated
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Frequently Asked Questions
When switch allkeys-lru → allkeys-lfu?
When your workload has a clear hot/cold partition (some keys read forever, others rarely). LFU wins for classic skewed workload.
Redis in production without persistence?
Fine for pure cache (session, counter). If the data cannot be regenerated, enable AOF everysec.
Sharding or Cluster?
Redis Cluster — built-in sharding (up to 1000 nodes). For < 100 GB sentinel + application-level sharding is more common.