merge: Improve the OpenDC compute model (#37)

This pull request contains various improvements to the OpenDC compute simulation model.

- Support filtering hosts based on CPU capacity
- Do not allocate lambda in fast-path
- Redesign VM interference algorithm
- Report provisioning time of virtual machines
- Prevent allocations during collection cycle 
- Use correct flow input capacity for counters
- Support running workloads without coroutines

**Breaking API Changes**

- `VirtualMachine` now requires `cpuCapacity` parameter.
- `VmInterferenceModel` needs to be constructed using `VmInterferenceModel.Builder` and can't be passed a list of groups anymore.
- Scheduling latency is not collected anymore. Instead, use the boot time and provisioning time to derive the scheduling latency.
- Telemetry data is recorded using `*TableReader` interfaces as opposed to the `*Data` classes. These classes are re-used per row and should not be shared with other threads, since the underlying data may change.
- `SimMachine` does not implement `AutoCloseable` anymore. Machines can be removed from a `SimHypervisor` using the `removeMachine` method.
- `SimMachine.run` is moved to an extension method called `runWorkload`. Users can now also choose to run a workload using the asynchronous `SimMachine.startWorkload`.

11 files changed, 178 insertions, 128 deletions

diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadLoader.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadLoader.kt
index 1a6624f7..f23becda 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadLoader.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadLoader.kt
@@ -92,7 +92,8 @@ public class ComputeWorkloadLoader(private val baseDir: File) {
         val idCol = reader.resolve(RESOURCE_ID)
         val startTimeCol = reader.resolve(RESOURCE_START_TIME)
         val stopTimeCol = reader.resolve(RESOURCE_STOP_TIME)
-        val coresCol = reader.resolve(RESOURCE_CPU_COUNT)
+        val cpuCountCol = reader.resolve(RESOURCE_CPU_COUNT)
+        val cpuCapacityCol = reader.resolve(RESOURCE_CPU_CAPACITY)
         val memCol = reader.resolve(RESOURCE_MEM_CAPACITY)
 
         var counter = 0
@@ -108,8 +109,9 @@ public class ComputeWorkloadLoader(private val baseDir: File) {
 
                 val submissionTime = reader.get(startTimeCol) as Instant
                 val endTime = reader.get(stopTimeCol) as Instant
-                val maxCores = reader.getInt(coresCol)
-                val requiredMemory = reader.getDouble(memCol) / 1000.0 // Convert from KB to MB
+                val cpuCount = reader.getInt(cpuCountCol)
+                val cpuCapacity = reader.getDouble(cpuCapacityCol)
+                val memCapacity = reader.getDouble(memCol) / 1000.0 // Convert from KB to MB
                 val uid = UUID.nameUUIDFromBytes("$id-${counter++}".toByteArray())
 
                 val builder = fragments.getValue(id)
@@ -119,8 +121,9 @@ public class ComputeWorkloadLoader(private val baseDir: File) {
                     VirtualMachine(
                         uid,
                         id,
-                        maxCores,
-                        requiredMemory.roundToLong(),
+                        cpuCount,
+                        cpuCapacity,
+                        memCapacity.roundToLong(),
                         totalLoad,
                         submissionTime,
                         endTime,
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadRunner.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadRunner.kt
index 283f82fe..90ee56cb 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadRunner.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/ComputeWorkloadRunner.kt
@@ -128,7 +128,8 @@ public class ComputeWorkloadRunner(
                             client.newFlavor(
                                 entry.name,
                                 entry.cpuCount,
-                                entry.memCapacity
+                                entry.memCapacity,
+                                meta = if (entry.cpuCapacity > 0.0) mapOf("cpu-capacity" to entry.cpuCapacity) else emptyMap()
                             ),
                             meta = mapOf("workload" to workload)
                         )
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/VirtualMachine.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/VirtualMachine.kt
index 5dd239f6..88e80719 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/VirtualMachine.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/VirtualMachine.kt
@@ -31,8 +31,9 @@ import java.util.*
  *
  * @param uid The unique identifier of the virtual machine.
  * @param name The name of the virtual machine.
+ * @param cpuCapacity The required CPU capacity for the VM in MHz.
  * @param cpuCount The number of vCPUs in the VM.
- * @param memCapacity The provisioned memory for the VM.
+ * @param memCapacity The provisioned memory for the VM in MB.
  * @param startTime The start time of the VM.
  * @param stopTime The stop time of the VM.
  * @param trace The trace that belong to this VM.
@@ -41,6 +42,7 @@ public data class VirtualMachine(
     val uid: UUID,
     val name: String,
     val cpuCount: Int,
+    val cpuCapacity: Double,
     val memCapacity: Long,
     val totalLoad: Double,
     val startTime: Instant,
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetComputeMetricExporter.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetComputeMetricExporter.kt
index ad182d67..a46885f4 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetComputeMetricExporter.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetComputeMetricExporter.kt
@@ -25,9 +25,9 @@ package org.opendc.compute.workload.export.parquet
 import io.opentelemetry.sdk.common.CompletableResultCode
 import org.opendc.telemetry.compute.ComputeMetricExporter
 import org.opendc.telemetry.compute.ComputeMonitor
-import org.opendc.telemetry.compute.table.HostData
-import org.opendc.telemetry.compute.table.ServerData
-import org.opendc.telemetry.compute.table.ServiceData
+import org.opendc.telemetry.compute.table.HostTableReader
+import org.opendc.telemetry.compute.table.ServerTableReader
+import org.opendc.telemetry.compute.table.ServiceTableReader
 import java.io.File
 
 /**
@@ -49,16 +49,16 @@ public class ParquetComputeMetricExporter(base: File, partition: String, bufferS
         bufferSize
     )
 
-    override fun record(data: ServerData) {
-        serverWriter.write(data)
+    override fun record(reader: ServerTableReader) {
+        serverWriter.write(reader)
     }
 
-    override fun record(data: HostData) {
-        hostWriter.write(data)
+    override fun record(reader: HostTableReader) {
+        hostWriter.write(reader)
     }
 
-    override fun record(data: ServiceData) {
-        serviceWriter.write(data)
+    override fun record(reader: ServiceTableReader) {
+        serviceWriter.write(reader)
     }
 
     override fun shutdown(): CompletableResultCode {
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetDataWriter.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetDataWriter.kt
index 4172d729..84387bbc 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetDataWriter.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetDataWriter.kt
@@ -50,9 +50,9 @@ public abstract class ParquetDataWriter<in T>(
     private val logger = KotlinLogging.logger {}
 
     /**
-     * The queue of commands to process.
+     * The queue of records to process.
      */
-    private val queue: BlockingQueue<T> = ArrayBlockingQueue(bufferSize)
+    private val queue: BlockingQueue<GenericData.Record> = ArrayBlockingQueue(bufferSize)
 
     /**
      * An exception to be propagated to the actual writer.
@@ -72,20 +72,20 @@ public abstract class ParquetDataWriter<in T>(
         }
 
         val queue = queue
-        val buf = mutableListOf<T>()
+        val buf = mutableListOf<GenericData.Record>()
         var shouldStop = false
 
         try {
             while (!shouldStop) {
                 try {
-                    process(writer, queue.take())
+                    writer.write(queue.take())
                 } catch (e: InterruptedException) {
                     shouldStop = true
                 }
 
                 if (queue.drainTo(buf) > 0) {
                     for (data in buf) {
-                        process(writer, data)
+                        writer.write(data)
                     }
                     buf.clear()
                 }
@@ -119,7 +119,9 @@ public abstract class ParquetDataWriter<in T>(
             throw IllegalStateException("Writer thread failed", exception)
         }
 
-        queue.put(data)
+        val builder = GenericRecordBuilder(schema)
+        convert(builder, data)
+        queue.put(builder.build())
     }
 
     /**
@@ -133,13 +135,4 @@ public abstract class ParquetDataWriter<in T>(
     init {
         writerThread.start()
     }
-
-    /**
-     * Process the specified [data] to be written to the Parquet file.
-     */
-    private fun process(writer: ParquetWriter<GenericData.Record>, data: T) {
-        val builder = GenericRecordBuilder(schema)
-        convert(builder, data)
-        writer.write(builder.build())
-    }
 }
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetHostDataWriter.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetHostDataWriter.kt
index 98a0739e..2b7cac8f 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetHostDataWriter.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetHostDataWriter.kt
@@ -28,17 +28,17 @@ import org.apache.avro.generic.GenericData
 import org.apache.avro.generic.GenericRecordBuilder
 import org.apache.parquet.avro.AvroParquetWriter
 import org.apache.parquet.hadoop.ParquetWriter
-import org.opendc.telemetry.compute.table.HostData
+import org.opendc.telemetry.compute.table.HostTableReader
 import org.opendc.trace.util.parquet.TIMESTAMP_SCHEMA
 import org.opendc.trace.util.parquet.UUID_SCHEMA
 import org.opendc.trace.util.parquet.optional
 import java.io.File
 
 /**
- * A Parquet event writer for [HostData]s.
+ * A Parquet event writer for [HostTableReader]s.
  */
 public class ParquetHostDataWriter(path: File, bufferSize: Int) :
-    ParquetDataWriter<HostData>(path, SCHEMA, bufferSize) {
+    ParquetDataWriter<HostTableReader>(path, SCHEMA, bufferSize) {
 
     override fun buildWriter(builder: AvroParquetWriter.Builder<GenericData.Record>): ParquetWriter<GenericData.Record> {
         return builder
@@ -46,7 +46,7 @@ public class ParquetHostDataWriter(path: File, bufferSize: Int) :
             .build()
     }
 
-    override fun convert(builder: GenericRecordBuilder, data: HostData) {
+    override fun convert(builder: GenericRecordBuilder, data: HostTableReader) {
         builder["timestamp"] = data.timestamp.toEpochMilli()
 
         builder["host_id"] = data.host.id
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServerDataWriter.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServerDataWriter.kt
index 0d11ec23..144b6624 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServerDataWriter.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServerDataWriter.kt
@@ -28,17 +28,17 @@ import org.apache.avro.generic.GenericData
 import org.apache.avro.generic.GenericRecordBuilder
 import org.apache.parquet.avro.AvroParquetWriter
 import org.apache.parquet.hadoop.ParquetWriter
-import org.opendc.telemetry.compute.table.ServerData
+import org.opendc.telemetry.compute.table.ServerTableReader
 import org.opendc.trace.util.parquet.TIMESTAMP_SCHEMA
 import org.opendc.trace.util.parquet.UUID_SCHEMA
 import org.opendc.trace.util.parquet.optional
 import java.io.File
 
 /**
- * A Parquet event writer for [ServerData]s.
+ * A Parquet event writer for [ServerTableReader]s.
  */
 public class ParquetServerDataWriter(path: File, bufferSize: Int) :
-    ParquetDataWriter<ServerData>(path, SCHEMA, bufferSize) {
+    ParquetDataWriter<ServerTableReader>(path, SCHEMA, bufferSize) {
 
     override fun buildWriter(builder: AvroParquetWriter.Builder<GenericData.Record>): ParquetWriter<GenericData.Record> {
         return builder
@@ -47,7 +47,7 @@ public class ParquetServerDataWriter(path: File, bufferSize: Int) :
             .build()
     }
 
-    override fun convert(builder: GenericRecordBuilder, data: ServerData) {
+    override fun convert(builder: GenericRecordBuilder, data: ServerTableReader) {
         builder["timestamp"] = data.timestamp.toEpochMilli()
 
         builder["server_id"] = data.server.id
@@ -55,9 +55,8 @@ public class ParquetServerDataWriter(path: File, bufferSize: Int) :
 
         builder["uptime"] = data.uptime
         builder["downtime"] = data.downtime
-        val bootTime = data.bootTime
-        builder["boot_time"] = bootTime?.toEpochMilli()
-        builder["scheduling_latency"] = data.schedulingLatency
+        builder["boot_time"] = data.bootTime?.toEpochMilli()
+        builder["provision_time"] = data.provisionTime?.toEpochMilli()
 
         builder["cpu_count"] = data.server.cpuCount
         builder["cpu_limit"] = data.cpuLimit
@@ -81,8 +80,8 @@ public class ParquetServerDataWriter(path: File, bufferSize: Int) :
             .name("host_id").type(UUID_SCHEMA.optional()).noDefault()
             .requiredLong("uptime")
             .requiredLong("downtime")
+            .name("provision_time").type(TIMESTAMP_SCHEMA.optional()).noDefault()
             .name("boot_time").type(TIMESTAMP_SCHEMA.optional()).noDefault()
-            .requiredLong("scheduling_latency")
             .requiredInt("cpu_count")
             .requiredDouble("cpu_limit")
             .requiredLong("cpu_time_active")
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServiceDataWriter.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServiceDataWriter.kt
index 47824b29..ec8a2b65 100644
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServiceDataWriter.kt
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/export/parquet/ParquetServiceDataWriter.kt
@@ -25,17 +25,17 @@ package org.opendc.compute.workload.export.parquet
 import org.apache.avro.Schema
 import org.apache.avro.SchemaBuilder
 import org.apache.avro.generic.GenericRecordBuilder
-import org.opendc.telemetry.compute.table.ServiceData
+import org.opendc.telemetry.compute.table.ServiceTableReader
 import org.opendc.trace.util.parquet.TIMESTAMP_SCHEMA
 import java.io.File
 
 /**
- * A Parquet event writer for [ServiceData]s.
+ * A Parquet event writer for [ServiceTableReader]s.
  */
 public class ParquetServiceDataWriter(path: File, bufferSize: Int) :
-    ParquetDataWriter<ServiceData>(path, SCHEMA, bufferSize) {
+    ParquetDataWriter<ServiceTableReader>(path, SCHEMA, bufferSize) {
 
-    override fun convert(builder: GenericRecordBuilder, data: ServiceData) {
+    override fun convert(builder: GenericRecordBuilder, data: ServiceTableReader) {
         builder["timestamp"] = data.timestamp.toEpochMilli()
         builder["hosts_up"] = data.hostsUp
         builder["hosts_down"] = data.hostsDown
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/PerformanceInterferenceReader.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/PerformanceInterferenceReader.kt
deleted file mode 100644
index 67f9626c..00000000
--- a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/PerformanceInterferenceReader.kt
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * Copyright (c) 2021 AtLarge Research
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-
-package org.opendc.compute.workload.util
-
-import com.fasterxml.jackson.annotation.JsonProperty
-import com.fasterxml.jackson.databind.ObjectMapper
-import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
-import com.fasterxml.jackson.module.kotlin.readValue
-import org.opendc.simulator.compute.kernel.interference.VmInterferenceGroup
-import java.io.File
-import java.io.InputStream
-
-/**
- * A parser for the JSON performance interference setup files used for the TPDS article on Capelin.
- */
-public class PerformanceInterferenceReader {
-    /**
-     * The [ObjectMapper] to use.
-     */
-    private val mapper = jacksonObjectMapper()
-
-    init {
-        mapper.addMixIn(VmInterferenceGroup::class.java, GroupMixin::class.java)
-    }
-
-    /**
-     * Read the performance interface model from [file].
-     */
-    public fun read(file: File): List<VmInterferenceGroup> {
-        return mapper.readValue(file)
-    }
-
-    /**
-     * Read the performance interface model from the input.
-     */
-    public fun read(input: InputStream): List<VmInterferenceGroup> {
-        return mapper.readValue(input)
-    }
-
-    private data class GroupMixin(
-        @JsonProperty("minServerLoad")
-        val targetLoad: Double,
-        @JsonProperty("performanceScore")
-        val score: Double,
-        @JsonProperty("vms")
-        val members: Set<String>,
-    )
-}
diff --git a/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/VmInterferenceModelReader.kt b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/VmInterferenceModelReader.kt
new file mode 100644
index 00000000..e0fa8904
--- /dev/null
+++ b/opendc-compute/opendc-compute-workload/src/main/kotlin/org/opendc/compute/workload/util/VmInterferenceModelReader.kt
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.compute.workload.util
+
+import com.fasterxml.jackson.annotation.JsonProperty
+import com.fasterxml.jackson.core.JsonParseException
+import com.fasterxml.jackson.core.JsonParser
+import com.fasterxml.jackson.core.JsonToken
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import org.opendc.simulator.compute.kernel.interference.VmInterferenceModel
+import java.io.File
+import java.io.InputStream
+
+/**
+ * A parser for the JSON performance interference setup files used for the TPDS article on Capelin.
+ */
+public class VmInterferenceModelReader {
+    /**
+     * The [ObjectMapper] to use.
+     */
+    private val mapper = jacksonObjectMapper()
+
+    /**
+     * Read the performance interface model from [file].
+     */
+    public fun read(file: File): VmInterferenceModel {
+        val builder = VmInterferenceModel.builder()
+        val parser = mapper.createParser(file)
+        parseGroups(parser, builder)
+        return builder.build()
+    }
+
+    /**
+     * Read the performance interface model from the input.
+     */
+    public fun read(input: InputStream): VmInterferenceModel {
+        val builder = VmInterferenceModel.builder()
+        val parser = mapper.createParser(input)
+        parseGroups(parser, builder)
+        return builder.build()
+    }
+
+    /**
+     * Parse all groups in an interference JSON file.
+     */
+    private fun parseGroups(parser: JsonParser, builder: VmInterferenceModel.Builder) {
+        parser.nextToken()
+
+        if (!parser.isExpectedStartArrayToken) {
+            throw JsonParseException(parser, "Expected array at start, but got ${parser.currentToken()}")
+        }
+
+        while (parser.nextToken() != JsonToken.END_ARRAY) {
+            parseGroup(parser, builder)
+        }
+    }
+
+    /**
+     * Parse a group an interference JSON file.
+     */
+    private fun parseGroup(parser: JsonParser, builder: VmInterferenceModel.Builder) {
+        var targetLoad = Double.POSITIVE_INFINITY
+        var score = 1.0
+        val members = mutableSetOf<String>()
+
+        if (!parser.isExpectedStartObjectToken) {
+            throw JsonParseException(parser, "Expected object, but got ${parser.currentToken()}")
+        }
+
+        while (parser.nextValue() != JsonToken.END_OBJECT) {
+            when (parser.currentName) {
+                "vms" -> parseGroupMembers(parser, members)
+                "minServerLoad" -> targetLoad = parser.doubleValue
+                "performanceScore" -> score = parser.doubleValue
+            }
+        }
+
+        builder.addGroup(members, targetLoad, score)
+    }
+
+    /**
+     * Parse the members of a group.
+     */
+    private fun parseGroupMembers(parser: JsonParser, members: MutableSet<String>) {
+        if (!parser.isExpectedStartArrayToken) {
+            throw JsonParseException(parser, "Expected array for group members, but got ${parser.currentToken()}")
+        }
+
+        while (parser.nextValue() != JsonToken.END_ARRAY) {
+            if (parser.currentToken() != JsonToken.VALUE_STRING) {
+                throw JsonParseException(parser, "Expected string value for group member")
+            }
+
+            val member = parser.text.removePrefix("vm__workload__").removeSuffix(".txt")
+            members.add(member)
+        }
+    }
+
+    private data class Group(
+        @JsonProperty("minServerLoad")
+        val targetLoad: Double,
+        @JsonProperty("performanceScore")
+        val score: Double,
+        @JsonProperty("vms")
+        val members: Set<String>,
+    )
+}
diff --git a/opendc-compute/opendc-compute-workload/src/test/kotlin/org/opendc/compute/workload/util/PerformanceInterferenceReaderTest.kt b/opendc-compute/opendc-compute-workload/src/test/kotlin/org/opendc/compute/workload/util/VmInterferenceModelReaderTest.kt
index c79f0584..1c3e7149 100644
--- a/opendc-compute/opendc-compute-workload/src/test/kotlin/org/opendc/compute/workload/util/PerformanceInterferenceReaderTest.kt
+++ b/opendc-compute/opendc-compute-workload/src/test/kotlin/org/opendc/compute/workload/util/VmInterferenceModelReaderTest.kt
@@ -22,24 +22,16 @@
 
 package org.opendc.compute.workload.util
 
-import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertAll
+import org.junit.jupiter.api.assertDoesNotThrow
 
 /**
- * Test suite for the [PerformanceInterferenceReader] class.
+ * Test suite for the [VmInterferenceModelReader] class.
  */
-class PerformanceInterferenceReaderTest {
+class VmInterferenceModelReaderTest {
     @Test
     fun testSmoke() {
-        val input = checkNotNull(PerformanceInterferenceReader::class.java.getResourceAsStream("/perf-interference.json"))
-        val result = PerformanceInterferenceReader().read(input)
-
-        assertAll(
-            { assertEquals(2, result.size) },
-            { assertEquals(setOf("vm_a", "vm_c", "vm_x", "vm_y"), result[0].members) },
-            { assertEquals(0.0, result[0].targetLoad, 0.001) },
-            { assertEquals(0.8830158730158756, result[0].score, 0.001) }
-        )
+        val input = checkNotNull(VmInterferenceModelReader::class.java.getResourceAsStream("/perf-interference.json"))
+        assertDoesNotThrow { VmInterferenceModelReader().read(input) }
     }
 }