llm: Avoid underflow in free memory logging

If a GPU's free memory is less than the reserved amount, we might get
an underflow. Since it is an unsigned uint64, we print this as a large
number rather than the more correct 0. This only affects logging, the
actual layout code already handles this correctly.

Bug #12138

llm/server.go

@@ -678,8 +678,12 @@ func (s *ollamaServer) Load(ctx context.Context, gpus discover.GpuInfoList, requ
 
 	if !(len(gpus) == 1 && gpus[0].Library == "cpu") {
 		for _, gpu := range gpus {
+			available := gpu.FreeMemory - envconfig.GpuOverhead() - gpu.MinimumMemory
+			if gpu.FreeMemory < envconfig.GpuOverhead()+gpu.MinimumMemory {
+				available = 0
+			}
 			slog.Info("gpu memory", "id", gpu.ID,
-				"available", format.HumanBytes2(gpu.FreeMemory-envconfig.GpuOverhead()-gpu.MinimumMemory),
+				"available", format.HumanBytes2(available),
 				"free", format.HumanBytes2(gpu.FreeMemory),
 				"minimum", format.HumanBytes2(gpu.MinimumMemory),
 				"overhead", format.HumanBytes2(envconfig.GpuOverhead()))