Memory overhead

MemoryBenchmark estimates are performed using Java Agent for Memory Measurements and Java Object Layout to calculate the runtime size. The size may be affected by compressed references, object padding, etc. as determined by the JVM.

By forking Java 5's ConcurrentHashMap, Guava has a slight advantage with per-entry optimizations. This is especially evident when weak and soft reference caching is used. Caffeine must retain additional fields to remove a collected entry due to decorating a Java 8 ConcurrentHashMap.

Caffeine may lazily initialize or dynamically resize its internal data structures based on usage. This reduces the footprint in favor of using additional memory only as required to meet usage demands (e.g. throughput).

Unbounded

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	262,288 bytes	32 bytes (32 aligned)	524,504 bytes	32 bytes (32 aligned)
Guava	263,008 bytes	48 bytes (48 aligned)	263,200 bytes	48 bytes (48 aligned)

Maximum Size

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	787,728 bytes	64 bytes (64 aligned)	787,848 bytes	64 bytes (64 aligned)
Guava	263,360 bytes	64 bytes (64 aligned)	263,608 bytes	64 bytes (64 aligned)

Maximum Size & Expire after Access

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	787,760 bytes	72 bytes (72 aligned)	787,904 bytes	72 bytes (72 aligned)
Guava	263,360 bytes	64 bytes (64 aligned)	263,608 bytes	64 bytes (64 aligned)

Maximum Size & Expire after Write

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	787,792 bytes	80 bytes (80 aligned)	787,936 bytes	80 bytes (80 aligned)
Guava	263,520 bytes	80 bytes (80 aligned)	263,776 bytes	80 bytes (80 aligned)

Maximum Size & Refresh after Write

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	787,768 bytes	72 bytes (72 aligned)	787,912 bytes	72 bytes (72 aligned)
Guava	263,376 bytes	80 bytes (80 aligned)	263,656 bytes	80 bytes (80 aligned)

Maximum Weight

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	525,624 bytes	72 bytes (72 aligned)	525,672 bytes	72 bytes (72 aligned)
Guava	263,376 bytes	64 bytes (64 aligned)	263,600 bytes	64 bytes (64 aligned)

Expire after Access

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,288 bytes	72 bytes (72 aligned)	263,432 bytes	72 bytes (72 aligned)
Guava	263,360 bytes	64 bytes (64 aligned)	263,608 bytes	64 bytes (64 aligned)

Expire after Write

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,256 bytes	72 bytes (72 aligned)	263,424 bytes	72 bytes (72 aligned)
Guava	263,168 bytes	64 bytes (64 aligned)	263,416 bytes	64 bytes (64 aligned)

Expire after Access & after Write

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,336 bytes	88 bytes (88 aligned)	263,480 bytes	88 bytes (88 aligned)
Guava	263,520 bytes	80 bytes (80 aligned)	263,776 bytes	80 bytes (80 aligned)

Weak Keys

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,272 bytes	72 bytes (72 aligned)	263,392 bytes	88 bytes (88 aligned)
Guava	263,216 bytes	40 bytes (40 aligned)	263,480 bytes	56 bytes (56 aligned)

Weak Values

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,264 bytes	64 bytes (64 aligned)	263,384 bytes	80 bytes (80 aligned)
Guava	263,216 bytes	48 bytes (48 aligned)	263,480 bytes	64 bytes (64 aligned)

Weak Keys & Weak Values

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,312 bytes	80 bytes (80 aligned)	263,432 bytes	112 bytes (112 aligned)
Guava	263,392 bytes	40 bytes (40 aligned)	263,584 bytes	72 bytes (72 aligned)

Weak Keys & Soft Values

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,312 bytes	88 bytes (88 aligned)	263,432 bytes	120 bytes (120 aligned)
Guava	263,392 bytes	48 bytes (48 aligned)	263,656 bytes	80 bytes (80 aligned)

Soft Values

Cache	Baseline (MemoryMeter)	Per Entry (MemoryMeter)	Baseline (ObjectLayout)	Per Entry (ObjectLayout)
Caffeine	263,264 bytes	72 bytes (72 aligned)	263,384 bytes	88 bytes (88 aligned)
Guava	263,216 bytes	56 bytes (56 aligned)	263,480 bytes	72 bytes (72 aligned)