Performance Considerations

1. GOMAXPROCS Setting

go
import "runtime"

func main() {
    // Get number of logical CPUs
    numCPU := runtime.NumCPU()
    fmt.Printf("Number of CPUs: %d\n", numCPU)
    
    // Set GOMAXPROCS (default is NumCPU since Go 1.5)
    runtime.GOMAXPROCS(numCPU)
    
    // Or set via environment variable:
    // GOMAXPROCS=4 go run main.go
}

2. Goroutine Overhead

go
// Benchmark: Cost of creating goroutines
func BenchmarkGoroutineCreation(b *testing.B) {
    for i := 0; i < b.N; i++ {
        var wg sync.WaitGroup
        wg.Add(1)
        go func() {
            wg.Done()
        }()
        wg.Wait()
    }
}
// Result: ~1-2 microseconds per goroutine

3. When NOT to Use Goroutines

go
// ❌ Overkill for simple tasks
for _, item := range items {
    go processItem(item) // Too much overhead for small items
}

// ✅ Better: Process in batches
func processBatch(items []Item) {
    const batchSize = 100
    for i := 0; i < len(items); i += batchSize {
        end := i + batchSize
        if end > len(items) {
            end = len(items)
        }
        go processBatchInternal(items[i:end])
    }
}

4. Profiling Goroutines

go
import (
    "net/http"
    _ "net/http/pprof"
    "runtime"
)

func main() {
    go func() {
        http.ListenAndServe("localhost:6060", nil)
    }()
    
    // Check goroutine count
    fmt.Printf("Number of goroutines: %d\n", runtime.NumGoroutine())
    
    // View in browser:
    // http://localhost:6060/debug/pprof/goroutine
}