simulator: Add the CPU power model from iCanCloud/E-mc2

This change implements the CPU energy model with p-states from iCanCloud/E-mc2:

- Only pushed a portion of the code for discussion as not sure if the idea is
  on track.
- Inline comments have been added, and formal documents will follow once the
  model is finalized.
- The p-state power consumptions are currently hard-coded in a companion
  object, which should be improved in the next PR(s).

**Breaking Changes**

- CpuPowerModel: directly interact with the machine it is measuring.
- SimBareMetalMachine: expose the speeds of its CPU cores and its clock
  instant.

2 files changed, 47 insertions, 6 deletions

diff --git a/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/CpuPowerModelTest.kt b/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/CpuPowerModelTest.kt
index 9d034a5d..cd18b120 100644
--- a/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/CpuPowerModelTest.kt
+++ b/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/CpuPowerModelTest.kt
@@ -8,7 +8,6 @@ import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.Arguments
 import org.junit.jupiter.params.provider.MethodSource
-import org.opendc.compute.simulator.SimHost
 import org.opendc.compute.simulator.power.api.CpuPowerModel
 import org.opendc.compute.simulator.power.models.*
 import org.opendc.simulator.compute.SimBareMetalMachine
@@ -18,7 +17,7 @@ import kotlin.math.pow
 @OptIn(ExperimentalCoroutinesApi::class)
 internal class CpuPowerModelTest {
     private val epsilon = 10.0.pow(-3)
-    private val cpuUtil = .9
+    private val cpuUtil = 0.9
 
     @ParameterizedTest
     @MethodSource("cpuPowerModelArgs")
@@ -49,12 +48,10 @@ internal class CpuPowerModelTest {
     ) {
         runBlockingTest {
             val cpuLoads = flowOf(cpuUtil, cpuUtil, cpuUtil).stateIn(this)
-            val bareMetalDriver = mockkClass(SimHost::class)
             val machine = mockkClass(SimBareMetalMachine::class)
-            every { bareMetalDriver.machine } returns machine
             every { machine.usage } returns cpuLoads
 
-            val serverPowerDraw = powerModel.getPowerDraw(bareMetalDriver)
+            val serverPowerDraw = powerModel.getPowerDraw(machine)
 
             assertEquals(
                 serverPowerDraw.first().toDouble(),
@@ -62,7 +59,6 @@ internal class CpuPowerModelTest {
                 epsilon
             )
 
-            verify(exactly = 1) { bareMetalDriver.machine }
             verify(exactly = 1) { machine.usage }
         }
     }
diff --git a/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/PStatePowerModelTest.kt b/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/PStatePowerModelTest.kt
new file mode 100644
index 00000000..e144e541
--- /dev/null
+++ b/simulator/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/power/PStatePowerModelTest.kt
@@ -0,0 +1,45 @@
+package org.opendc.compute.simulator.power
+
+import io.mockk.*
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.opendc.compute.simulator.power.models.PStatePowerModel
+import org.opendc.simulator.compute.SimBareMetalMachine
+import java.time.Clock
+
+internal class PStatePowerModelTest {
+    @Test
+    fun `update CPU power meter with P-states`() {
+        val p0Power = 8.0
+        val p3Power = 94.0
+        val p4Power = 103.0
+        val expectedP0Power = 8.0 * 10
+        val expectedP0P4Power = expectedP0Power + 103.0 * 10
+
+        val clock = mockkClass(Clock::class)
+        val machine = mockkClass(SimBareMetalMachine::class)
+        every { clock.millis() } returnsMany listOf(0L, 0L, 10_000L, 20_000L)
+        every { machine.speed } returns
+            listOf(2.8, 2.8, 2.8, 2.8).map { it * 1000 } andThen // Max. 2.8MHz covered by P0
+            listOf(1.5, 3.1, 3.3, 3.6).map { it * 1000 } andThen // Max. 3.6MHz covered by P4
+            listOf(1.5, 3.1, 3.1, 3.3).map { it * 1000 } // Max. 3.3MHz covered by P3
+
+        // Power meter initialization.
+        val pStatePowerModel = PStatePowerModel(machine, clock)
+        verify(exactly = 2) { clock.millis() }
+        verify(exactly = 1) { machine.speed }
+        assertEquals(p0Power, pStatePowerModel.getInstantCpuPower())
+
+        // The first measure.
+        pStatePowerModel.updateCpuPowerMeter()
+        assertEquals(p4Power, pStatePowerModel.getInstantCpuPower())
+        assertEquals(expectedP0Power, pStatePowerModel.getAccumulatedCpuPower())
+
+        // The second measure.
+        pStatePowerModel.updateCpuPowerMeter()
+        assertEquals(p3Power, pStatePowerModel.getInstantCpuPower())
+        assertEquals(expectedP0P4Power, pStatePowerModel.getAccumulatedCpuPower())
+
+        verify(exactly = 4) { clock.millis() }
+    }
+}