FreeCache - A cache library for Go with zero GC overhead and high concurrent performance.
Long lived objects in memory introduce expensive GC overhead, With FreeCache, you can cache unlimited number of objects in memory
without increased latency and degraded throughput.
Features
- Store hundreds of millions of entries
- Zero GC overhead
- High concurrent thread-safe access
- Pure Go implementation
- Expiration support
- Nearly LRU algorithm
- Strictly limited memory usage
- Come with a toy server that supports a few basic Redis commands with pipeline
- Iterator support
Performance
Here is the benchmark result compares to built-in map, Set performance is about 2x faster than built-in map, Get performance is about 1/2x slower than built-in map. Since it is single threaded benchmark, in multi-threaded environment,
FreeCache should be many times faster than single lock protected built-in map.
BenchmarkCacheSet 3000000 446 ns/op
BenchmarkMapSet 2000000 861 ns/op
BenchmarkCacheGet 3000000 517 ns/op
BenchmarkMapGet 10000000 212 ns/op
Example Usage
cacheSize := 100 * 1024 * 1024
cache := freecache.NewCache(cacheSize)
debug.SetGCPercent(20)
key := []byte("abc")
val := []byte("def")
expire := 60 // expire in 60 seconds
cache.Set(key, val, expire)
got, err := cache.Get(key)
if err != nil {
fmt.Println(err)
} else {
fmt.Println(string(got))
}
affected := cache.Del(key)
fmt.Println("deleted key ", affected)
fmt.Println("entry count ", cache.EntryCount())
Notice
- Memory is preallocated.
- If you allocate large amount of memory, you may need to set
debug.SetGCPercent()
to a much lower percentage to get a normal GC frequency.
How it is done
FreeCache avoids GC overhead by reducing the number of pointers.
No matter how many entries stored in it, there are only 512 pointers.
The data set is sharded into 256 segments by the hash value of the key.
Each segment has only two pointers, one is the ring buffer that stores keys and values,
the other one is the index slice which used to lookup for an entry.
Each segment has its own lock, so it supports high concurrent access.
TODO
- Support dump to file and load from file.
- Support resize cache size at runtime.
License
The MIT License