Fast resizable golang semaphore based on CAS
- allows weighted acquire/release;
- supports cancellation via context;
- allows change semaphore limit after creation;
- faster than channel based semaphores.
Initiate
import "github.com/marusama/semaphore/v2"
...
sem := semaphore.New(5) // new semaphore with limit = 5Acquire
sem.Acquire(ctx, n) // acquire n with context
sem.TryAcquire(n) // try acquire n without blocking
...
ctx := context.WithTimeout(context.Background(), time.Second)
sem.Acquire(ctx, n) // acquire n with timeoutRelease
sem.Release(n) // release nChange semaphore limit
sem.SetLimit(new_limit) // set new semaphore limitRun on MacBook Pro (2017) with 3,1GHz Core i5 cpu and 8GB DDR3 ram, macOS High Sierra, go version go1.11.4 darwin/amd64:
// this semaphore:
BenchmarkSemaphore_Acquire_Release_under_limit_simple-4 20000000 98.6 ns/op 96 B/op 1 allocs/op
BenchmarkSemaphore_Acquire_Release_under_limit-4 1000000 1593 ns/op 960 B/op 10 allocs/op
BenchmarkSemaphore_Acquire_Release_over_limit-4 100000 20760 ns/op 9600 B/op 100 allocs/op
// some other implementations:
// golang.org/x/sync/semaphore:
BenchmarkXSyncSemaphore_Acquire_Release_under_limit_simple-4 50000000 34.9 ns/op 0 B/op 0 allocs/op
BenchmarkXSyncSemaphore_Acquire_Release_under_limit-4 1000000 1103 ns/op 0 B/op 0 allocs/op
BenchmarkXSyncSemaphore_Acquire_Release_over_limit-4 30000 65927 ns/op 15985 B/op 299 allocs/op
// github.com/abiosoft/semaphore:
BenchmarkAbiosoftSemaphore_Acquire_Release_under_limit_simple-4 10000000 208 ns/op 0 B/op 0 allocs/op
BenchmarkAbiosoftSemaphore_Acquire_Release_under_limit-4 500000 3147 ns/op 0 B/op 0 allocs/op
BenchmarkAbiosoftSemaphore_Acquire_Release_over_limit-4 50000 37148 ns/op 0 B/op 0 allocs/op
// github.com/dropbox/godropbox
BenchmarkDropboxBoundedSemaphore_Acquire_Release_under_limit_simple-4 20000000 75.9 ns/op 0 B/op 0 allocs/op
BenchmarkDropboxBoundedSemaphore_Acquire_Release_under_limit-4 2000000 629 ns/op 0 B/op 0 allocs/op
BenchmarkDropboxBoundedSemaphore_Acquire_Release_over_limit-4 200000 27308 ns/op 0 B/op 0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_under_limit_simple-4 50000000 39.7 ns/op 0 B/op 0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_under_limit-4 1000000 1170 ns/op 0 B/op 0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_over_limit-4 100000 21013 ns/op 0 B/op 0 allocs/op
// github.com/kamilsk/semaphore
BenchmarkKamilskSemaphore_Acquire_Release_under_limit_simple-4 20000000 110 ns/op 16 B/op 1 allocs/op
BenchmarkKamilskSemaphore_Acquire_Release_under_limit-4 1000000 1520 ns/op 160 B/op 10 allocs/op
BenchmarkKamilskSemaphore_Acquire_Release_over_limit-4 50000 42693 ns/op 1600 B/op 100 allocs/op
// github.com/pivotal-golang/semaphore
BenchmarkPivotalGolangSemaphore_Acquire_Release_under_limit_simple-4 3000000 558 ns/op 136 B/op 2 allocs/op
BenchmarkPivotalGolangSemaphore_Acquire_Release_under_limit-4 200000 9530 ns/op 1280 B/op 20 allocs/op
BenchmarkPivotalGolangSemaphore_Acquire_Release_over_limit-4 10000 111264 ns/op 12801 B/op 200 allocs/op
You can rerun these benchmarks, just checkout benchmarks branch and run go test -bench=. -benchmem ./bench/...