feat: benchmark suite for decode speed, TTFT, and concurrent throughput

BenchmarkDecode, BenchmarkTTFT, BenchmarkConcurrent across 3 models.
Uses testing.B with b.ReportMetric for Go benchstat integration.

Co-Authored-By: Virgil <virgil@lethean.io>

rocm_benchmark_test.go

@@ -0,0 +1,181 @@
+//go:build rocm
+
+package rocm
+
+import (
+	"context"
+	"os"
+	"sync"
+	"testing"
+	"time"
+
+	"forge.lthn.ai/core/go-inference"
+)
+
+// benchModels lists the models to benchmark.
+// Each loads ~3-9 GB of VRAM, so they run sequentially (one at a time).
+var benchModels = []struct {
+	name string
+	path string
+}{
+	{"Gemma3-4B-Q4_K_M", "/data/lem/gguf/LEK-Gemma3-4B-Q4_K_M.gguf"},
+	{"Llama3.1-8B-Q4_K_M", "/data/lem/gguf/LEK-Llama-3.1-8B-Q4_K_M.gguf"},
+	{"Qwen2.5-7B-Q4_K_M", "/data/lem/gguf/LEK-Qwen-2.5-7B-Q4_K_M.gguf"},
+}
+
+func skipBenchIfUnavailable(b *testing.B) {
+	b.Helper()
+	if _, err := os.Stat("/dev/kfd"); err != nil {
+		b.Skip("no ROCm hardware")
+	}
+	if _, err := findLlamaServer(); err != nil {
+		b.Skip("llama-server not found")
+	}
+}
+
+// loadBenchModel loads a model for benchmarking. Caller must defer m.Close().
+// Stops the benchmark timer during loading so load time is excluded.
+func loadBenchModel(b *testing.B, path string, opts ...inference.LoadOption) inference.TextModel {
+	b.Helper()
+	if _, err := os.Stat(path); err != nil {
+		b.Skipf("model not available: %s", path)
+	}
+
+	b.StopTimer()
+	backend := &rocmBackend{}
+	defaults := []inference.LoadOption{inference.WithContextLen(2048)}
+	m, err := backend.LoadModel(path, append(defaults, opts...)...)
+	if err != nil {
+		b.Fatalf("load model: %v", err)
+	}
+
+	if vram, err := GetVRAMInfo(); err == nil {
+		b.Logf("VRAM after load: %d MiB used / %d MiB total",
+			vram.Used/(1024*1024), vram.Total/(1024*1024))
+	}
+
+	b.StartTimer()
+	return m
+}
+
+// BenchmarkDecode measures token generation speed (tok/s).
+// Generates 128 tokens per iteration, reports tokens/second.
+func BenchmarkDecode(b *testing.B) {
+	skipBenchIfUnavailable(b)
+
+	for _, model := range benchModels {
+		b.Run(model.name, func(b *testing.B) {
+			m := loadBenchModel(b, model.path)
+			defer m.Close()
+
+			const maxTok = 128
+
+			var totalTokens int
+			b.ResetTimer()
+			for range b.N {
+				ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+				var count int
+				for range m.Generate(ctx, "Explain the theory of relativity in detail.", inference.WithMaxTokens(maxTok)) {
+					count++
+				}
+				cancel()
+				totalTokens += count
+			}
+			b.StopTimer()
+
+			if totalTokens > 0 {
+				elapsed := b.Elapsed()
+				tokPerSec := float64(totalTokens) / elapsed.Seconds()
+				b.ReportMetric(tokPerSec, "tok/s")
+			}
+		})
+	}
+}
+
+// BenchmarkTTFT measures time-to-first-token latency.
+// Reports the average time from request start to first token received.
+func BenchmarkTTFT(b *testing.B) {
+	skipBenchIfUnavailable(b)
+
+	for _, model := range benchModels {
+		b.Run(model.name, func(b *testing.B) {
+			m := loadBenchModel(b, model.path)
+			defer m.Close()
+
+			var totalTTFT time.Duration
+			b.ResetTimer()
+			for range b.N {
+				ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+				start := time.Now()
+				for range m.Generate(ctx, "Hello", inference.WithMaxTokens(1)) {
+					totalTTFT += time.Since(start)
+				}
+				cancel()
+			}
+			b.StopTimer()
+
+			if b.N > 0 {
+				avgTTFT := totalTTFT / time.Duration(b.N)
+				b.ReportMetric(float64(avgTTFT.Microseconds()), "µs/first-tok")
+			}
+		})
+	}
+}
+
+// BenchmarkConcurrent measures throughput with multiple goroutines.
+// Uses 4 parallel slots and 4 goroutines generating simultaneously.
+func BenchmarkConcurrent(b *testing.B) {
+	skipBenchIfUnavailable(b)
+
+	for _, model := range benchModels {
+		b.Run(model.name, func(b *testing.B) {
+			m := loadBenchModel(b, model.path, inference.WithParallelSlots(4))
+			defer m.Close()
+
+			const numWorkers = 4
+			const maxTok = 32
+
+			prompts := []string{
+				"The capital of France is",
+				"The capital of Germany is",
+				"The capital of Italy is",
+				"The capital of Spain is",
+			}
+
+			var totalTokens int
+			b.ResetTimer()
+			for range b.N {
+				var wg sync.WaitGroup
+				var mu sync.Mutex
+				iterTokens := 0
+
+				wg.Add(numWorkers)
+				for i := range numWorkers {
+					go func(idx int) {
+						defer wg.Done()
+						ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+						defer cancel()
+
+						count := 0
+						for range m.Generate(ctx, prompts[idx], inference.WithMaxTokens(maxTok)) {
+							count++
+						}
+
+						mu.Lock()
+						iterTokens += count
+						mu.Unlock()
+					}(i)
+				}
+				wg.Wait()
+				totalTokens += iterTokens
+			}
+			b.StopTimer()
+
+			if totalTokens > 0 {
+				elapsed := b.Elapsed()
+				b.ReportMetric(float64(totalTokens)/elapsed.Seconds(), "tok/s-aggregate")
+				b.ReportMetric(float64(totalTokens)/float64(b.N), "tok/iter")
+			}
+		})
+	}
+}