merge: Migrate to flow-based simulation for low-level models

This pull request converts the `opendc-simulator-resources` module into a flow
simulator and adapts the existing low-level models (e.g., CPU, network, disk)
to this new flow simulator.

The flow simulator works differently from the uniform resource consumption
model, in that it models flow through a system of connections, as opposed to
resource consumptions. Concretely, this means that while in the uniform
resource consumption model, consumptions with the same usage are propagated to
the resources, in the flow simulator, only changes to the flow in the system
are propagated. 

Overall, this leads to less updates in the system and therefore higher
performance. The benchmarks shows that the new implementation obtains more than
double the performance of the old implementation. We have focused in the new
implementation on reducing the amount of work and memory
allocations/loads/stores per updates.

* Migrate from kotlinx-benchmark to jmh-gradle (for better profiling support)
* Use longer traces for benchmarks (to prevent measuring the benchmark
overhead)
* Use direct field access for perf-sensitive code
* Combine work and deadline to duration
* Add support for pushing flow from context (to eliminate the allocation for
every `SimResourceCommand`)
* Reduce memory allocations in SimResourceInterpreter, by revamping the way
timers are allocated.
* Simplify max-min aggregator implementation (by utilizing the new push
mechanism) 
* Invoke consumer callback on every invalidation (in order to propagate changes
downstream)
* Lazily push changes to resource context (by not updating the flow rate
immediately after a push, but only after an update)
* Remove onUpdate callback 
* Merge distributor and aggregator into switch 
* Separate push and pull flags 
* Remove failure callback from FlowSource 
* Create separate callbacks for remaining events 
* Make convergence callback optional
* Reduce field accesses in FlowConsumerContextImpl
* Optimize hot path in SimTraceWorkload
* Expose CPU time counters directly on hypervisor 
* Optimize telemetry collection

**Breaking API Changes**

* The entire `opendc-simulator-resources` module has been replaced by the
`opendc-simulator-flow` module.
* `SimHypervisor.Listener` has been removed in favour of a new interface that
exposes the performance counters of the hypervisor directly. To listen for
convergence, use `FlowConvergenceListener`.

6 files changed, 78 insertions, 122 deletions

diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/SimMachineTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/SimMachineTest.kt
index 81268879..0bb24ed8 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/SimMachineTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/SimMachineTest.kt
@@ -34,10 +34,10 @@ import org.opendc.simulator.compute.workload.SimFlopsWorkload
 import org.opendc.simulator.compute.workload.SimWorkload
 import org.opendc.simulator.compute.workload.SimWorkloadLifecycle
 import org.opendc.simulator.core.runBlockingSimulation
+import org.opendc.simulator.flow.FlowEngine
+import org.opendc.simulator.flow.source.FixedFlowSource
 import org.opendc.simulator.network.SimNetworkSink
 import org.opendc.simulator.power.SimPowerSource
-import org.opendc.simulator.resources.SimResourceInterpreter
-import org.opendc.simulator.resources.consumer.SimWorkConsumer
 
 /**
  * Test suite for the [SimBareMetalMachine] class.
@@ -60,7 +60,7 @@ class SimMachineTest {
     @Test
     fun testFlopsWorkload() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -83,7 +83,7 @@ class SimMachineTest {
             memory = List(4) { MemoryUnit("Crucial", "MTA18ASF4G72AZ-3G2B1", 3200.0, 32_000) }
         )
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -100,13 +100,13 @@ class SimMachineTest {
 
     @Test
     fun testPower() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter,
+            engine,
             machineModel,
             SimplePowerDriver(LinearPowerModel(100.0, 50.0))
         )
-        val source = SimPowerSource(interpreter, capacity = 1000.0)
+        val source = SimPowerSource(engine, capacity = 1000.0)
         source.connect(machine.psu)
 
         try {
@@ -125,7 +125,7 @@ class SimMachineTest {
     @Test
     fun testCapacityClamp() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -151,7 +151,7 @@ class SimMachineTest {
     @Test
     fun testMemory() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -171,7 +171,7 @@ class SimMachineTest {
     @Test
     fun testMemoryUsage() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -180,7 +180,7 @@ class SimMachineTest {
             machine.run(object : SimWorkload {
                 override fun onStart(ctx: SimMachineContext) {
                     val lifecycle = SimWorkloadLifecycle(ctx)
-                    ctx.memory.startConsumer(lifecycle.waitFor(SimWorkConsumer(ctx.memory.capacity, utilization = 0.8)))
+                    ctx.memory.startConsumer(lifecycle.waitFor(FixedFlowSource(ctx.memory.capacity, utilization = 0.8)))
                 }
             })
 
@@ -192,22 +192,22 @@ class SimMachineTest {
 
     @Test
     fun testNetUsage() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter,
+            engine,
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
 
         val adapter = (machine.peripherals[0] as SimNetworkAdapter)
-        adapter.connect(SimNetworkSink(interpreter, adapter.bandwidth))
+        adapter.connect(SimNetworkSink(engine, adapter.bandwidth))
 
         try {
             machine.run(object : SimWorkload {
                 override fun onStart(ctx: SimMachineContext) {
                     val lifecycle = SimWorkloadLifecycle(ctx)
                     val iface = ctx.net[0]
-                    iface.tx.startConsumer(lifecycle.waitFor(SimWorkConsumer(iface.bandwidth, utilization = 0.8)))
+                    iface.tx.startConsumer(lifecycle.waitFor(FixedFlowSource(iface.bandwidth, utilization = 0.8)))
                 }
             })
 
@@ -219,9 +219,9 @@ class SimMachineTest {
 
     @Test
     fun testDiskReadUsage() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter,
+            engine,
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -231,7 +231,7 @@ class SimMachineTest {
                 override fun onStart(ctx: SimMachineContext) {
                     val lifecycle = SimWorkloadLifecycle(ctx)
                     val disk = ctx.storage[0]
-                    disk.read.startConsumer(lifecycle.waitFor(SimWorkConsumer(disk.read.capacity, utilization = 0.8)))
+                    disk.read.startConsumer(lifecycle.waitFor(FixedFlowSource(disk.read.capacity, utilization = 0.8)))
                 }
             })
 
@@ -243,9 +243,9 @@ class SimMachineTest {
 
     @Test
     fun testDiskWriteUsage() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter,
+            engine,
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -255,7 +255,7 @@ class SimMachineTest {
                 override fun onStart(ctx: SimMachineContext) {
                     val lifecycle = SimWorkloadLifecycle(ctx)
                     val disk = ctx.storage[0]
-                    disk.write.startConsumer(lifecycle.waitFor(SimWorkConsumer(disk.write.capacity, utilization = 0.8)))
+                    disk.write.startConsumer(lifecycle.waitFor(FixedFlowSource(disk.write.capacity, utilization = 0.8)))
                 }
             })
 
@@ -268,7 +268,7 @@ class SimMachineTest {
     @Test
     fun testCancellation() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -290,7 +290,7 @@ class SimMachineTest {
     @Test
     fun testConcurrentRuns() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -313,7 +313,7 @@ class SimMachineTest {
     @Test
     fun testClose() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/device/SimPsuTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/device/SimPsuTest.kt
index 6c9ec7bd..e5b509f0 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/device/SimPsuTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/device/SimPsuTest.kt
@@ -29,8 +29,8 @@ import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
 import org.opendc.simulator.compute.power.PowerDriver
 import org.opendc.simulator.core.runBlockingSimulation
+import org.opendc.simulator.flow.FlowEngine
 import org.opendc.simulator.power.SimPowerSource
-import org.opendc.simulator.resources.SimResourceInterpreter
 
 /**
  * Test suite for [SimPsu]
@@ -55,8 +55,8 @@ internal class SimPsuTest {
         val ratedOutputPower = 240.0
         val energyEfficiency = mapOf(0.0 to 1.0)
 
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
-        val source = SimPowerSource(interpreter, capacity = ratedOutputPower)
+        val engine = FlowEngine(coroutineContext, clock)
+        val source = SimPowerSource(engine, capacity = ratedOutputPower)
 
         val cpuLogic = mockk<PowerDriver.Logic>()
         every { cpuLogic.computePower() } returns 0.0
@@ -78,8 +78,8 @@ internal class SimPsuTest {
             1.0 to 0.94,
         )
 
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
-        val source = SimPowerSource(interpreter, capacity = ratedOutputPower)
+        val engine = FlowEngine(coroutineContext, clock)
+        val source = SimPowerSource(engine, capacity = ratedOutputPower)
 
         val cpuLogic = mockk<PowerDriver.Logic>()
         every { cpuLogic.computePower() } returnsMany listOf(50.0, 100.0, 150.0, 200.0)
diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimHypervisorTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimFairShareHypervisorTest.kt
index 1f010338..9db2e6ec 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimHypervisorTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimFairShareHypervisorTest.kt
@@ -40,13 +40,13 @@ import org.opendc.simulator.compute.power.ConstantPowerModel
 import org.opendc.simulator.compute.power.SimplePowerDriver
 import org.opendc.simulator.compute.workload.SimTraceWorkload
 import org.opendc.simulator.core.runBlockingSimulation
-import org.opendc.simulator.resources.SimResourceInterpreter
+import org.opendc.simulator.flow.FlowEngine
 
 /**
  * Test suite for the [SimHypervisor] class.
  */
 @OptIn(ExperimentalCoroutinesApi::class)
-internal class SimHypervisorTest {
+internal class SimFairShareHypervisorTest {
     private lateinit var model: MachineModel
 
     @BeforeEach
@@ -63,26 +63,6 @@ internal class SimHypervisorTest {
      */
     @Test
     fun testOvercommittedSingle() = runBlockingSimulation {
-        val listener = object : SimHypervisor.Listener {
-            var totalRequestedWork = 0.0
-            var totalGrantedWork = 0.0
-            var totalOvercommittedWork = 0.0
-
-            override fun onSliceFinish(
-                hypervisor: SimHypervisor,
-                totalWork: Double,
-                grantedWork: Double,
-                overcommittedWork: Double,
-                interferedWork: Double,
-                cpuUsage: Double,
-                cpuDemand: Double
-            ) {
-                totalRequestedWork += totalWork
-                totalGrantedWork += grantedWork
-                totalOvercommittedWork += overcommittedWork
-            }
-        }
-
         val duration = 5 * 60L
         val workloadA =
             SimTraceWorkload(
@@ -94,24 +74,26 @@ internal class SimHypervisorTest {
                 ),
             )
 
-        val platform = SimResourceInterpreter(coroutineContext, clock)
+        val platform = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(platform, model, SimplePowerDriver(ConstantPowerModel(0.0)))
-        val hypervisor = SimFairShareHypervisor(platform, scalingGovernor = PerformanceScalingGovernor(), listener = listener)
+        val hypervisor = SimFairShareHypervisor(platform, null, PerformanceScalingGovernor(), null)
 
         launch {
             machine.run(hypervisor)
             println("Hypervisor finished")
         }
         yield()
+
         val vm = hypervisor.createMachine(model)
         vm.run(workloadA)
+
         yield()
         machine.close()
 
         assertAll(
-            { assertEquals(1113300.0, listener.totalRequestedWork, "Requested Burst does not match") },
-            { assertEquals(1023300.0, listener.totalGrantedWork, "Granted Burst does not match") },
-            { assertEquals(90000.0, listener.totalOvercommittedWork, "Overcommissioned Burst does not match") },
+            { assertEquals(319781, hypervisor.counters.cpuActiveTime, "Active time does not match") },
+            { assertEquals(880219, hypervisor.counters.cpuIdleTime, "Idle time does not match") },
+            { assertEquals(28125, hypervisor.counters.cpuStealTime, "Steal time does not match") },
             { assertEquals(1200000, clock.millis()) { "Current time is correct" } }
         )
     }
@@ -121,26 +103,6 @@ internal class SimHypervisorTest {
      */
     @Test
     fun testOvercommittedDual() = runBlockingSimulation {
-        val listener = object : SimHypervisor.Listener {
-            var totalRequestedWork = 0.0
-            var totalGrantedWork = 0.0
-            var totalOvercommittedWork = 0.0
-
-            override fun onSliceFinish(
-                hypervisor: SimHypervisor,
-                totalWork: Double,
-                grantedWork: Double,
-                overcommittedWork: Double,
-                interferedWork: Double,
-                cpuUsage: Double,
-                cpuDemand: Double
-            ) {
-                totalRequestedWork += totalWork
-                totalGrantedWork += grantedWork
-                totalOvercommittedWork += overcommittedWork
-            }
-        }
-
         val duration = 5 * 60L
         val workloadA =
             SimTraceWorkload(
@@ -161,11 +123,11 @@ internal class SimHypervisorTest {
                 )
             )
 
-        val platform = SimResourceInterpreter(coroutineContext, clock)
+        val platform = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
             platform, model, SimplePowerDriver(ConstantPowerModel(0.0))
         )
-        val hypervisor = SimFairShareHypervisor(platform, listener = listener)
+        val hypervisor = SimFairShareHypervisor(platform, null, null, null)
 
         launch {
             machine.run(hypervisor)
@@ -187,9 +149,9 @@ internal class SimHypervisorTest {
         yield()
 
         assertAll(
-            { assertEquals(2073600.0, listener.totalRequestedWork, "Requested Burst does not match") },
-            { assertEquals(1053600.0, listener.totalGrantedWork, "Granted Burst does not match") },
-            { assertEquals(1020000.0, listener.totalOvercommittedWork, "Overcommissioned Burst does not match") },
+            { assertEquals(329250, hypervisor.counters.cpuActiveTime, "Active time does not match") },
+            { assertEquals(870750, hypervisor.counters.cpuIdleTime, "Idle time does not match") },
+            { assertEquals(318750, hypervisor.counters.cpuStealTime, "Steal time does not match") },
             { assertEquals(1200000, clock.millis()) }
         )
     }
@@ -202,11 +164,9 @@ internal class SimHypervisorTest {
             memory = List(4) { MemoryUnit("Crucial", "MTA18ASF4G72AZ-3G2B1", 3200.0, 32_000) }
         )
 
-        val platform = SimResourceInterpreter(coroutineContext, clock)
-        val machine = SimBareMetalMachine(
-            platform, model, SimplePowerDriver(ConstantPowerModel(0.0))
-        )
-        val hypervisor = SimFairShareHypervisor(platform)
+        val platform = FlowEngine(coroutineContext, clock)
+        val machine = SimBareMetalMachine(platform, model, SimplePowerDriver(ConstantPowerModel(0.0)))
+        val hypervisor = SimFairShareHypervisor(platform, null, null, null)
 
         assertDoesNotThrow {
             launch {
@@ -232,11 +192,11 @@ internal class SimHypervisorTest {
         )
         val interferenceModel = VmInterferenceModel(groups)
 
-        val platform = SimResourceInterpreter(coroutineContext, clock)
+        val platform = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
             platform, model, SimplePowerDriver(ConstantPowerModel(0.0))
         )
-        val hypervisor = SimFairShareHypervisor(platform, interferenceDomain = interferenceModel.newDomain())
+        val hypervisor = SimFairShareHypervisor(platform, null, null, interferenceModel.newDomain())
 
         val duration = 5 * 60L
         val workloadA =
diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimSpaceSharedHypervisorTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimSpaceSharedHypervisorTest.kt
index 3d3feb2a..b05ffd22 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimSpaceSharedHypervisorTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/kernel/SimSpaceSharedHypervisorTest.kt
@@ -40,7 +40,7 @@ import org.opendc.simulator.compute.workload.SimFlopsWorkload
 import org.opendc.simulator.compute.workload.SimRuntimeWorkload
 import org.opendc.simulator.compute.workload.SimTraceWorkload
 import org.opendc.simulator.core.runBlockingSimulation
-import org.opendc.simulator.resources.SimResourceInterpreter
+import org.opendc.simulator.flow.FlowEngine
 
 /**
  * A test suite for the [SimSpaceSharedHypervisor].
@@ -74,11 +74,9 @@ internal class SimSpaceSharedHypervisorTest {
                 ),
             )
 
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
-        val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock), machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
-        )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val engine = FlowEngine(coroutineContext, clock)
+        val machine = SimBareMetalMachine(engine, machineModel, SimplePowerDriver(ConstantPowerModel(0.0)))
+        val hypervisor = SimSpaceSharedHypervisor(engine, null, null)
 
         launch { machine.run(hypervisor) }
         val vm = hypervisor.createMachine(machineModel)
@@ -98,11 +96,9 @@ internal class SimSpaceSharedHypervisorTest {
     fun testRuntimeWorkload() = runBlockingSimulation {
         val duration = 5 * 60L * 1000
         val workload = SimRuntimeWorkload(duration)
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
-        val machine = SimBareMetalMachine(
-            interpreter, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
-        )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val engine = FlowEngine(coroutineContext, clock)
+        val machine = SimBareMetalMachine(engine, machineModel, SimplePowerDriver(ConstantPowerModel(0.0)))
+        val hypervisor = SimSpaceSharedHypervisor(engine, null, null)
 
         launch { machine.run(hypervisor) }
         yield()
@@ -121,11 +117,11 @@ internal class SimSpaceSharedHypervisorTest {
     fun testFlopsWorkload() = runBlockingSimulation {
         val duration = 5 * 60L * 1000
         val workload = SimFlopsWorkload((duration * 3.2).toLong(), 1.0)
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
+            engine, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
         )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val hypervisor = SimSpaceSharedHypervisor(engine, null, null)
 
         launch { machine.run(hypervisor) }
         yield()
@@ -142,11 +138,11 @@ internal class SimSpaceSharedHypervisorTest {
     @Test
     fun testTwoWorkloads() = runBlockingSimulation {
         val duration = 5 * 60L * 1000
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val engine = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
-            interpreter, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
+            engine, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
         )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val hypervisor = SimSpaceSharedHypervisor(engine, null, null)
 
         launch { machine.run(hypervisor) }
         yield()
@@ -155,6 +151,8 @@ internal class SimSpaceSharedHypervisorTest {
         vm.run(SimRuntimeWorkload(duration))
         vm.close()
 
+        yield()
+
         val vm2 = hypervisor.createMachine(machineModel)
         vm2.run(SimRuntimeWorkload(duration))
         vm2.close()
@@ -168,11 +166,9 @@ internal class SimSpaceSharedHypervisorTest {
      */
     @Test
     fun testConcurrentWorkloadFails() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
-        val machine = SimBareMetalMachine(
-            interpreter, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
-        )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val engine = FlowEngine(coroutineContext, clock)
+        val machine = SimBareMetalMachine(engine, machineModel, SimplePowerDriver(ConstantPowerModel(0.0)))
+        val hypervisor = SimSpaceSharedHypervisor(engine, null, null)
 
         launch { machine.run(hypervisor) }
         yield()
@@ -192,11 +188,11 @@ internal class SimSpaceSharedHypervisorTest {
      */
     @Test
     fun testConcurrentWorkloadSucceeds() = runBlockingSimulation {
-        val interpreter = SimResourceInterpreter(coroutineContext, clock)
+        val interpreter = FlowEngine(coroutineContext, clock)
         val machine = SimBareMetalMachine(
             interpreter, machineModel, SimplePowerDriver(ConstantPowerModel(0.0))
         )
-        val hypervisor = SimSpaceSharedHypervisor(interpreter)
+        val hypervisor = SimSpaceSharedHypervisor(interpreter, null, null)
 
         launch { machine.run(hypervisor) }
         yield()
diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/power/PStatePowerDriverTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/power/PStatePowerDriverTest.kt
index c39859bf..f557c8d3 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/power/PStatePowerDriverTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/power/PStatePowerDriverTest.kt
@@ -55,7 +55,7 @@ internal class PStatePowerDriverTest {
         val cpu = mockk<SimProcessingUnit>(relaxUnitFun = true)
 
         every { cpu.capacity } returns 3200.0
-        every { cpu.speed } returns 1200.0
+        every { cpu.rate } returns 1200.0
 
         val driver = PStatePowerDriver(
             sortedMapOf(
@@ -77,10 +77,10 @@ internal class PStatePowerDriverTest {
         val cpus = listOf(cpu, cpu)
 
         every { cpus[0].capacity } returns 1000.0
-        every { cpus[0].speed } returns 1200.0
+        every { cpus[0].rate } returns 1200.0
 
         every { cpus[1].capacity } returns 3500.0
-        every { cpus[1].speed } returns 1200.0
+        every { cpus[1].rate } returns 1200.0
 
         val driver = PStatePowerDriver(
             sortedMapOf(
@@ -112,11 +112,11 @@ internal class PStatePowerDriverTest {
 
         val logic = driver.createLogic(machine, listOf(cpu))
 
-        every { cpu.speed } returns 1400.0
+        every { cpu.rate } returns 1400.0
         every { cpu.capacity } returns 1400.0
         assertEquals(150.0, logic.computePower())
 
-        every { cpu.speed } returns 1400.0
+        every { cpu.rate } returns 1400.0
         every { cpu.capacity } returns 4000.0
         assertEquals(235.0, logic.computePower())
     }
diff --git a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/workload/SimTraceWorkloadTest.kt b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/workload/SimTraceWorkloadTest.kt
index 78019c2e..cdbffe4b 100644
--- a/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/workload/SimTraceWorkloadTest.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/test/kotlin/org/opendc/simulator/compute/workload/SimTraceWorkloadTest.kt
@@ -31,7 +31,7 @@ import org.opendc.simulator.compute.model.*
 import org.opendc.simulator.compute.power.ConstantPowerModel
 import org.opendc.simulator.compute.power.SimplePowerDriver
 import org.opendc.simulator.core.runBlockingSimulation
-import org.opendc.simulator.resources.SimResourceInterpreter
+import org.opendc.simulator.flow.FlowEngine
 
 /**
  * Test suite for the [SimTraceWorkloadTest] class.
@@ -52,7 +52,7 @@ class SimTraceWorkloadTest {
     @Test
     fun testSmoke() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -79,7 +79,7 @@ class SimTraceWorkloadTest {
     @Test
     fun testOffset() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -106,7 +106,7 @@ class SimTraceWorkloadTest {
     @Test
     fun testSkipFragment() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )
@@ -134,7 +134,7 @@ class SimTraceWorkloadTest {
     @Test
     fun testZeroCores() = runBlockingSimulation {
         val machine = SimBareMetalMachine(
-            SimResourceInterpreter(coroutineContext, clock),
+            FlowEngine(coroutineContext, clock),
             machineModel,
             SimplePowerDriver(ConstantPowerModel(0.0))
         )