Fix concurrency for CPU mode

Prior refactoring passes accidentally removed the logic to bypass VRAM
checks for CPU loads.  This adds that back, along with test coverage.

This also fixes loaded map access in the unit test to be behind the mutex which was
likely the cause of various flakes in the tests.

server/sched.go

@@ -149,6 +149,14 @@ func (s *Scheduler) processPending(ctx context.Context) {
 						break
 					}
 
+					// If we're CPU only mode, just limit by loadedMax above
+					// TODO handle system memory exhaustion
+					if (len(gpus) == 1 && gpus[0].Library == "cpu") || pending.opts.NumGPU == 0 {
+						slog.Debug("cpu mode with existing models, loading")
+						s.loadFn(pending, ggml, gpus)
+						break
+					}
+
 					// No models loaded. Load the model but prefer the best fit.
 					if loadedCount == 0 {
 						slog.Debug("loading first model", "model", pending.model.ModelPath)

server/sched_test.go

@@ -28,19 +28,33 @@ func TestInitScheduler(t *testing.T) {
 	ctx, done := context.WithCancel(context.Background())
 	defer done()
 	initialMax := loadedMax
+	initialParallel := numParallel
 	s := InitScheduler(ctx)
 	require.Equal(t, initialMax, loadedMax)
+	s.loadedMu.Lock()
 	require.NotNil(t, s.loaded)
+	s.loadedMu.Unlock()
 
 	os.Setenv("OLLAMA_MAX_LOADED_MODELS", "blue")
 	s = InitScheduler(ctx)
 	require.Equal(t, initialMax, loadedMax)
+	s.loadedMu.Lock()
 	require.NotNil(t, s.loaded)
+	s.loadedMu.Unlock()
 
 	os.Setenv("OLLAMA_MAX_LOADED_MODELS", "0")
 	s = InitScheduler(ctx)
 	require.Equal(t, 0, loadedMax)
+	s.loadedMu.Lock()
 	require.NotNil(t, s.loaded)
+	s.loadedMu.Unlock()
+
+	os.Setenv("OLLAMA_NUM_PARALLEL", "blue")
+	_ = InitScheduler(ctx)
+	require.Equal(t, initialParallel, numParallel)
+	os.Setenv("OLLAMA_NUM_PARALLEL", "10")
+	_ = InitScheduler(ctx)
+	require.Equal(t, 10, numParallel)
 }
 
 func TestLoad(t *testing.T) {
@@ -51,6 +65,7 @@ func TestLoad(t *testing.T) {
 	req := &LlmRequest{
 		ctx:             ctx,
 		model:           &Model{ModelPath: "foo"},
+		opts:            api.DefaultOptions(),
 		successCh:       make(chan *runnerRef, 1),
 		errCh:           make(chan error, 1),
 		sessionDuration: 2,
@@ -63,7 +78,9 @@ func TestLoad(t *testing.T) {
 	s.load(req, ggml, gpus)
 	require.Len(t, req.successCh, 0)
 	require.Len(t, req.errCh, 1)
+	s.loadedMu.Lock()
 	require.Len(t, s.loaded, 0)
+	s.loadedMu.Unlock()
 	err := <-req.errCh
 	require.Contains(t, err.Error(), "this model may be incompatible")
 
@@ -78,7 +95,9 @@ func TestLoad(t *testing.T) {
 	case resp := <-req.successCh:
 		require.Equal(t, uint64(10), resp.estimatedVRAM)
 		require.Equal(t, uint(1), resp.refCount)
+		s.loadedMu.Lock()
 		require.Len(t, s.loaded, 1)
+		s.loadedMu.Unlock()
 	}
 
 	req.model.ModelPath = "dummy_model_path"
@@ -90,7 +109,9 @@ func TestLoad(t *testing.T) {
 	case resp := <-req.successCh:
 		t.Errorf("unexpected success %v", resp)
 	}
+	s.loadedMu.Lock()
 	runner := s.loaded["dummy_model_path"]
+	s.loadedMu.Unlock()
 	require.NotNil(t, runner)
 	require.Equal(t, uint(0), runner.refCount)
 	time.Sleep(1 * time.Millisecond)
@@ -143,6 +164,7 @@ func newScenario(t *testing.T, ctx context.Context, modelName string, estimatedV
 	scenario.req = &LlmRequest{
 		ctx:             scenario.ctx,
 		model:           model,
+		opts:            api.DefaultOptions(),
 		sessionDuration: 5 * time.Millisecond,
 		successCh:       make(chan *runnerRef, 1),
 		errCh:           make(chan error, 1),
@@ -171,7 +193,9 @@ func TestRequests(t *testing.T) {
 	// Multiple loaded models
 	scenario3a := newScenario(t, ctx, "ollama-model-3a", 1*format.GigaByte)
 	scenario3b := newScenario(t, ctx, "ollama-model-3b", 24*format.GigaByte)
-	scenario3c := newScenario(t, ctx, "ollama-model-3c", 30) // Needs prior unloaded
+	scenario3c := newScenario(t, ctx, "ollama-model-4a", 30)
+	scenario3c.req.opts.NumGPU = 0                           // CPU load, will be allowed
+	scenario3d := newScenario(t, ctx, "ollama-model-3c", 30) // Needs prior unloaded
 
 	s := InitScheduler(ctx)
 	s.getGpuFn = func() gpu.GpuInfoList {
@@ -240,7 +264,9 @@ func TestRequests(t *testing.T) {
 	case <-ctx.Done():
 		t.Errorf("timeout")
 	}
+	s.loadedMu.Lock()
 	require.Len(t, s.loaded, 1)
+	s.loadedMu.Unlock()
 
 	loadedMax = 0
 	s.newServerFn = scenario3b.newServer
@@ -254,19 +280,14 @@ func TestRequests(t *testing.T) {
 	case <-ctx.Done():
 		t.Errorf("timeout")
 	}
+	s.loadedMu.Lock()
 	require.Len(t, s.loaded, 2)
+	s.loadedMu.Unlock()
 
-	// Try to load a model that wont fit
+	// This is a CPU load with NumGPU = 0 so it should load
 	s.newServerFn = scenario3c.newServer
 	slog.Info("scenario3c")
-	require.Len(t, s.loaded, 2)
-	scenario3a.ctxDone() // Won't help since this one isn't big enough to make room
-	time.Sleep(2 * time.Millisecond)
 	s.pendingReqCh <- scenario3c.req
-	// finish prior request, so new model can load
-	time.Sleep(6 * time.Millisecond)
-	require.Len(t, s.loaded, 1)
-	scenario3b.ctxDone()
 	select {
 	case resp := <-scenario3c.req.successCh:
 		require.Equal(t, resp.llama, scenario3c.srv)
@@ -275,7 +296,36 @@ func TestRequests(t *testing.T) {
 	case <-ctx.Done():
 		t.Errorf("timeout")
 	}
-	require.Len(t, s.loaded, 1)
+	s.loadedMu.Lock()
+	require.Len(t, s.loaded, 3)
+	s.loadedMu.Unlock()
+
+	// Try to load a model that wont fit
+	s.newServerFn = scenario3d.newServer
+	slog.Info("scenario3d")
+	s.loadedMu.Lock()
+	require.Len(t, s.loaded, 3)
+	s.loadedMu.Unlock()
+	scenario3a.ctxDone() // Won't help since this one isn't big enough to make room
+	time.Sleep(2 * time.Millisecond)
+	s.pendingReqCh <- scenario3d.req
+	// finish prior request, so new model can load
+	time.Sleep(6 * time.Millisecond)
+	s.loadedMu.Lock()
+	require.Len(t, s.loaded, 2)
+	s.loadedMu.Unlock()
+	scenario3b.ctxDone()
+	select {
+	case resp := <-scenario3d.req.successCh:
+		require.Equal(t, resp.llama, scenario3d.srv)
+		require.Len(t, s.pendingReqCh, 0)
+		require.Len(t, scenario3d.req.errCh, 0)
+	case <-ctx.Done():
+		t.Errorf("timeout")
+	}
+	s.loadedMu.Lock()
+	require.Len(t, s.loaded, 2)
+	s.loadedMu.Unlock()
 }
 
 func TestGetRunner(t *testing.T) {
@@ -318,7 +368,9 @@ func TestGetRunner(t *testing.T) {
 		t.Errorf("timeout")
 	}
 	scenario1a.ctxDone()
+	s.loadedMu.Lock()
 	require.Len(t, s.loaded, 1)
+	s.loadedMu.Unlock()
 
 	scenario1c.req.model.ModelPath = "bad path"
 	slog.Info("scenario1c")
@@ -328,7 +380,9 @@ func TestGetRunner(t *testing.T) {
 	require.Len(t, errCh1c, 0)
 
 	time.Sleep(5 * time.Millisecond)
+	s.loadedMu.Lock()
 	require.Len(t, s.loaded, 0)
+	s.loadedMu.Unlock()
 	require.Len(t, errCh1c, 1)
 	err = <-errCh1c
 	require.Contains(t, err.Error(), "bad path")
@@ -358,7 +412,9 @@ func TestPrematureExpired(t *testing.T) {
 		require.Equal(t, resp.llama, scenario1a.srv)
 		require.Len(t, s.pendingReqCh, 0)
 		require.Len(t, errCh1a, 0)
+		s.loadedMu.Lock()
 		require.Len(t, s.loaded, 1)
+		s.loadedMu.Unlock()
 		slog.Info("sending premature expired event now")
 		s.expiredCh <- resp // Shouldn't happen in real life, but make sure its safe
 	case <-ctx.Done():
@@ -383,6 +439,7 @@ func TestUseLoadedRunner(t *testing.T) {
 	ctx, done := context.WithTimeout(context.Background(), 5*time.Millisecond)
 	req := &LlmRequest{
 		ctx:             ctx,
+		opts:            api.DefaultOptions(),
 		successCh:       make(chan *runnerRef, 1),
 		sessionDuration: 2,
 	}
@@ -426,8 +483,10 @@ func TestUpdateFreeSpace(t *testing.T) {
 	r2 := &runnerRef{llama: llm2, gpus: gpus}
 
 	s := InitScheduler(ctx)
+	s.loadedMu.Lock()
 	s.loaded["a"] = r1
 	s.loaded["b"] = r2
+	s.loadedMu.Unlock()
 
 	s.updateFreeSpace(gpus)
 	require.Equal(t, uint64(850), gpus[0].FreeMemory)
@@ -437,13 +496,18 @@ func TestUpdateFreeSpace(t *testing.T) {
 func TestFindRunnerToUnload(t *testing.T) {
 	ctx, done := context.WithTimeout(context.Background(), 5*time.Millisecond)
 	defer done()
-	req := &LlmRequest{ctx: ctx}
+	req := &LlmRequest{
+		ctx:  ctx,
+		opts: api.DefaultOptions(),
+	}
 	r1 := &runnerRef{refCount: 1, sessionDuration: 1}
 	r2 := &runnerRef{sessionDuration: 2}
 
 	s := InitScheduler(ctx)
+	s.loadedMu.Lock()
 	s.loaded["a"] = r1
 	s.loaded["b"] = r2
+	s.loadedMu.Unlock()
 
 	resp := s.findRunnerToUnload(req)
 	require.Equal(t, r2, resp)
@@ -458,10 +522,11 @@ func TestNeedsReload(t *testing.T) {
 	defer done()
 
 	llm := &mockLlm{}
+	do := api.DefaultOptions()
 	runner := &runnerRef{
 		adapters:   []string{"adapter1"},
 		projectors: []string{"projector1"},
-		Options:    &api.Options{},
+		Options:    &do,
 		llama:      llm,
 	}
 	req := &LlmRequest{
@@ -469,7 +534,7 @@ func TestNeedsReload(t *testing.T) {
 			AdapterPaths:   []string{"adapter2"},
 			ProjectorPaths: []string{"projector2"},
 		},
-		opts: api.Options{},
+		opts: api.DefaultOptions(),
 	}
 	resp := runner.needsReload(ctx, req)
 	require.True(t, resp)
@@ -508,8 +573,10 @@ func TestUnloadAllRunners(t *testing.T) {
 	r1 := &runnerRef{llama: llm1}
 	r2 := &runnerRef{llama: llm2}
 
+	s.loadedMu.Lock()
 	s.loaded["a"] = r1
 	s.loaded["b"] = r2
+	s.loadedMu.Unlock()
 	s.unloadAllRunners()
 
 	require.True(t, llm1.closeCalled)