Allocation profiler (#290)

16 files changed, 439 insertions, 73 deletions

diff --git a/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java b/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
index cd00f0d..041cacf 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
@@ -33,6 +33,7 @@ import me.lucko.spark.common.command.tabcomplete.CompletionSupplier;
 import me.lucko.spark.common.command.tabcomplete.TabCompleter;
 import me.lucko.spark.common.sampler.Sampler;
 import me.lucko.spark.common.sampler.SamplerBuilder;
+import me.lucko.spark.common.sampler.SamplerMode;
 import me.lucko.spark.common.sampler.ThreadDumper;
 import me.lucko.spark.common.sampler.ThreadGrouper;
 import me.lucko.spark.common.sampler.async.AsyncSampler;
@@ -80,6 +81,7 @@ public class SamplerModule implements CommandModule {
                 .argumentUsage("start", "thread", "thread name")
                 .argumentUsage("start", "only-ticks-over", "tick length millis")
                 .argumentUsage("start", "interval", "interval millis")
+                .argumentUsage("start", "alloc", null)
                 .argumentUsage("stop", "", null)
                 .argumentUsage("cancel", "", null)
                 .executor(this::profiler)
@@ -94,7 +96,7 @@ public class SamplerModule implements CommandModule {
                         }
                         if (subCommand.equals("start")) {
                             opts = new ArrayList<>(Arrays.asList("--timeout", "--regex", "--combine-all",
-                                    "--not-combined", "--interval", "--only-ticks-over", "--force-java-sampler"));
+                                    "--not-combined", "--interval", "--only-ticks-over", "--force-java-sampler", "--alloc", "--alloc-live-only"));
                             opts.removeAll(arguments);
                             opts.add("--thread"); // allowed multiple times
                         }
@@ -166,9 +168,12 @@ public class SamplerModule implements CommandModule {
                     "Consider setting a timeout value over 30 seconds."));
         }
 
-        double intervalMillis = arguments.doubleFlag("interval");
-        if (intervalMillis <= 0) {
-            intervalMillis = 4;
+        SamplerMode mode = arguments.boolFlag("alloc") ? SamplerMode.ALLOCATION : SamplerMode.EXECUTION;
+        boolean allocLiveOnly = arguments.boolFlag("alloc-live-only");
+
+        double interval = arguments.doubleFlag("interval");
+        if (interval <= 0) {
+            interval = mode.defaultInterval();
         }
 
         boolean ignoreSleeping = arguments.boolFlag("ignore-sleeping");
@@ -213,23 +218,33 @@ public class SamplerModule implements CommandModule {
         resp.broadcastPrefixed(text("Starting a new profiler, please wait..."));
 
         SamplerBuilder builder = new SamplerBuilder();
+        builder.mode(mode);
         builder.threadDumper(threadDumper);
         builder.threadGrouper(threadGrouper);
         if (timeoutSeconds != -1) {
             builder.completeAfter(timeoutSeconds, TimeUnit.SECONDS);
         }
-        builder.samplingInterval(intervalMillis);
+        builder.samplingInterval(interval);
         builder.ignoreSleeping(ignoreSleeping);
         builder.ignoreNative(ignoreNative);
         builder.forceJavaSampler(forceJavaSampler);
+        builder.allocLiveOnly(allocLiveOnly);
         if (ticksOver != -1) {
             builder.ticksOver(ticksOver, tickHook);
         }
-        Sampler sampler = builder.start(platform);
+
+        Sampler sampler;
+        try {
+            sampler = builder.start(platform);
+        } catch (UnsupportedOperationException e) {
+            resp.replyPrefixed(text(e.getMessage(), RED));
+            return;
+        }
+
         platform.getSamplerContainer().setActiveSampler(sampler);
 
         resp.broadcastPrefixed(text()
-                .append(text("Profiler is now running!", GOLD))
+                .append(text((mode == SamplerMode.ALLOCATION ? "Allocation Profiler" : "Profiler") + " is now running!", GOLD))
                 .append(space())
                 .append(text("(" + (sampler instanceof AsyncSampler ? "async" : "built-in java") + ")", DARK_GRAY))
                 .build()
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/AbstractSampler.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/AbstractSampler.java
index e324fd3..5abe71f 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/AbstractSampler.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/AbstractSampler.java
@@ -126,6 +126,7 @@ public abstract class AbstractSampler implements Sampler {
 
     protected void writeMetadataToProto(SamplerData.Builder proto, SparkPlatform platform, CommandSender creator, String comment, DataAggregator dataAggregator) {
         SamplerMetadata.Builder metadata = SamplerMetadata.newBuilder()
+                .setSamplerMode(getMode().asProto())
                 .setPlatformMetadata(platform.getPlugin().getPlatformInfo().toData().toProto())
                 .setCreator(creator.toData().toProto())
                 .setStartTime(this.startTime)
@@ -187,7 +188,7 @@ public abstract class AbstractSampler implements Sampler {
 
         ClassSourceLookup.Visitor classSourceVisitor = ClassSourceLookup.createVisitor(classSourceLookup);
 
-        ProtoTimeEncoder timeEncoder = new ProtoTimeEncoder(data);
+        ProtoTimeEncoder timeEncoder = new ProtoTimeEncoder(getMode().valueTransformer(), data);
         int[] timeWindows = timeEncoder.getKeys();
         for (int timeWindow : timeWindows) {
             proto.addTimeWindows(timeWindow);
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
index 36a63f1..aaf4f38 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
@@ -65,6 +65,13 @@ public interface Sampler {
     boolean isRunningInBackground();
 
     /**
+     * Gets the sampler mode.
+     *
+     * @return the sampler mode
+     */
+    SamplerMode getMode();
+
+    /**
      * Gets a future to encapsulate the completion of the sampler
      *
      * @return a future
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerBuilder.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerBuilder.java
index ec635ef..7891a98 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerBuilder.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerBuilder.java
@@ -23,6 +23,7 @@ package me.lucko.spark.common.sampler;
 import me.lucko.spark.common.SparkPlatform;
 import me.lucko.spark.common.sampler.async.AsyncProfilerAccess;
 import me.lucko.spark.common.sampler.async.AsyncSampler;
+import me.lucko.spark.common.sampler.async.SampleCollector;
 import me.lucko.spark.common.sampler.java.JavaSampler;
 import me.lucko.spark.common.tick.TickHook;
 
@@ -34,10 +35,12 @@ import java.util.concurrent.TimeUnit;
 @SuppressWarnings("UnusedReturnValue")
 public class SamplerBuilder {
 
-    private double samplingInterval = 4; // milliseconds
+    private SamplerMode mode = SamplerMode.EXECUTION;
+    private double samplingInterval = -1;
     private boolean ignoreSleeping = false;
     private boolean ignoreNative = false;
     private boolean useAsyncProfiler = true;
+    private boolean allocLiveOnly = false;
     private long autoEndTime = -1;
     private boolean background = false;
     private ThreadDumper threadDumper = ThreadDumper.ALL;
@@ -49,6 +52,11 @@ public class SamplerBuilder {
     public SamplerBuilder() {
     }
 
+    public SamplerBuilder mode(SamplerMode mode) {
+        this.mode = mode;
+        return this;
+    }
+
     public SamplerBuilder samplingInterval(double samplingInterval) {
         this.samplingInterval = samplingInterval;
         return this;
@@ -98,7 +106,16 @@ public class SamplerBuilder {
         return this;
     }
 
-    public Sampler start(SparkPlatform platform) {
+    public SamplerBuilder allocLiveOnly(boolean allocLiveOnly) {
+        this.allocLiveOnly = allocLiveOnly;
+        return this;
+    }
+
+    public Sampler start(SparkPlatform platform) throws UnsupportedOperationException {
+        if (this.samplingInterval <= 0) {
+            throw new IllegalArgumentException("samplingInterval = " + this.samplingInterval);
+        }
+
         boolean onlyTicksOverMode = this.ticksOver != -1 && this.tickHook != null;
         boolean canUseAsyncProfiler = this.useAsyncProfiler &&
                 !onlyTicksOverMode &&
@@ -106,13 +123,22 @@ public class SamplerBuilder {
                 !(this.threadDumper instanceof ThreadDumper.Regex) &&
                 AsyncProfilerAccess.getInstance(platform).checkSupported(platform);
 
+        if (this.mode == SamplerMode.ALLOCATION && (!canUseAsyncProfiler || !AsyncProfilerAccess.getInstance(platform).checkAllocationProfilingSupported(platform))) {
+            throw new UnsupportedOperationException("Allocation profiling is not supported on your system. Check the console for more info.");
+        }
+
+        int interval = (int) (this.mode == SamplerMode.EXECUTION ?
+                this.samplingInterval * 1000d : // convert to microseconds
+                this.samplingInterval
+        );
 
-        int intervalMicros = (int) (this.samplingInterval * 1000d);
-        SamplerSettings settings = new SamplerSettings(intervalMicros, this.threadDumper, this.threadGrouper, this.autoEndTime, this.background);
+        SamplerSettings settings = new SamplerSettings(interval, this.threadDumper, this.threadGrouper, this.autoEndTime, this.background);
 
         Sampler sampler;
-        if (canUseAsyncProfiler) {
-            sampler = new AsyncSampler(platform, settings);
+        if (this.mode == SamplerMode.ALLOCATION) {
+            sampler = new AsyncSampler(platform, settings, new SampleCollector.Allocation(interval, this.allocLiveOnly));
+        } else if (canUseAsyncProfiler) {
+            sampler = new AsyncSampler(platform, settings, new SampleCollector.Execution(interval));
         } else if (onlyTicksOverMode) {
             sampler = new JavaSampler(platform, settings, this.ignoreSleeping, this.ignoreNative, this.tickHook, this.ticksOver);
         } else {
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerMode.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerMode.java
new file mode 100644
index 0000000..f9a6e41
--- /dev/null
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/SamplerMode.java
@@ -0,0 +1,74 @@
+/*
+ * This file is part of spark.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package me.lucko.spark.common.sampler;
+
+import me.lucko.spark.proto.SparkSamplerProtos.SamplerMetadata;
+
+import java.util.function.LongToDoubleFunction;
+
+public enum SamplerMode {
+
+    EXECUTION(
+            value -> {
+                // convert the duration from microseconds -> milliseconds
+                return value / 1000d;
+            },
+            4, // ms
+            SamplerMetadata.SamplerMode.EXECUTION
+    ),
+
+    ALLOCATION(
+            value -> {
+                // do nothing
+                return value;
+            },
+            524287, // 512 KiB
+            SamplerMetadata.SamplerMode.ALLOCATION
+    );
+
+    private final LongToDoubleFunction valueTransformer;
+    private final int defaultInterval;
+    private final SamplerMetadata.SamplerMode proto;
+
+    SamplerMode(LongToDoubleFunction valueTransformer, int defaultInterval, SamplerMetadata.SamplerMode proto) {
+        this.valueTransformer = valueTransformer;
+        this.defaultInterval = defaultInterval;
+        this.proto = proto;
+    }
+
+    public LongToDoubleFunction valueTransformer() {
+        return this.valueTransformer;
+    }
+
+    public int defaultInterval() {
+        return this.defaultInterval;
+    }
+
+    /**
+     * Gets the metadata enum instance for this sampler mode.
+     *
+     * @return proto metadata
+     */
+    public SamplerMetadata.SamplerMode asProto() {
+        return this.proto;
+    }
+
+}
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncDataAggregator.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncDataAggregator.java
index 402330a..b9a80e0 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncDataAggregator.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncDataAggregator.java
@@ -50,7 +50,7 @@ public class AsyncDataAggregator extends AbstractDataAggregator {
     public void insertData(ProfileSegment element, int window) {
         try {
             ThreadNode node = getNode(this.threadGrouper.getGroup(element.getNativeThreadId(), element.getThreadName()));
-            node.log(STACK_TRACE_DESCRIBER, element.getStackTrace(), element.getTime(), window);
+            node.log(STACK_TRACE_DESCRIBER, element.getStackTrace(), element.getValue(), window);
         } catch (Exception e) {
             e.printStackTrace();
         }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerAccess.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerAccess.java
index 1480650..5bee56f 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerAccess.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerAccess.java
@@ -61,6 +61,8 @@ public class AsyncProfilerAccess {
 
     /** The event to use for profiling */
     private final ProfilingEvent profilingEvent;
+    /** The event to use for allocation profiling */
+    private final ProfilingEvent allocationProfilingEvent;
 
     /** If profiler is null, contains the reason why setup failed */
     private final Exception setupException;
@@ -68,10 +70,16 @@ public class AsyncProfilerAccess {
     AsyncProfilerAccess(SparkPlatform platform) {
         AsyncProfiler profiler;
         ProfilingEvent profilingEvent = null;
+        ProfilingEvent allocationProfilingEvent = null;
         Exception setupException = null;
 
         try {
             profiler = load(platform);
+
+            if (isEventSupported(profiler, ProfilingEvent.ALLOC, false)) {
+                allocationProfilingEvent = ProfilingEvent.ALLOC;
+            }
+
             if (isEventSupported(profiler, ProfilingEvent.CPU, false)) {
                 profilingEvent = ProfilingEvent.CPU;
             } else if (isEventSupported(profiler, ProfilingEvent.WALL, true)) {
@@ -84,6 +92,7 @@ public class AsyncProfilerAccess {
 
         this.profiler = profiler;
         this.profilingEvent = profilingEvent;
+        this.allocationProfilingEvent = allocationProfilingEvent;
         this.setupException = setupException;
     }
 
@@ -98,6 +107,10 @@ public class AsyncProfilerAccess {
         return this.profilingEvent;
     }
 
+    public ProfilingEvent getAllocationProfilingEvent() {
+        return this.allocationProfilingEvent;
+    }
+
     public boolean checkSupported(SparkPlatform platform) {
         if (this.setupException != null) {
             if (this.setupException instanceof UnsupportedSystemException) {
@@ -116,6 +129,15 @@ public class AsyncProfilerAccess {
         return this.profiler != null;
     }
 
+    public boolean checkAllocationProfilingSupported(SparkPlatform platform) {
+        boolean supported = this.allocationProfilingEvent != null;
+        if (!supported && this.profiler != null) {
+            platform.getPlugin().log(Level.WARNING, "The allocation profiling mode is not supported on your system. This is most likely because Hotspot debug symbols are not available.");
+            platform.getPlugin().log(Level.WARNING, "To resolve, try installing the 'openjdk-11-dbg' or 'openjdk-8-dbg' package using your OS package manager.");
+        }
+        return supported;
+    }
+
     private static AsyncProfiler load(SparkPlatform platform) throws Exception {
         // check compatibility
         String os = System.getProperty("os.name").toLowerCase(Locale.ROOT).replace(" ", "");
@@ -183,7 +205,8 @@ public class AsyncProfilerAccess {
 
     enum ProfilingEvent {
         CPU(Events.CPU),
-        WALL(Events.WALL);
+        WALL(Events.WALL),
+        ALLOC(Events.ALLOC);
 
         private final String id;
 
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerJob.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerJob.java
index d74b75f..039d4ba 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerJob.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncProfilerJob.java
@@ -20,6 +20,8 @@
 
 package me.lucko.spark.common.sampler.async;
 
+import com.google.common.collect.ImmutableList;
+
 import me.lucko.spark.common.SparkPlatform;
 import me.lucko.spark.common.sampler.ThreadDumper;
 import me.lucko.spark.common.sampler.async.jfr.JfrReader;
@@ -29,8 +31,8 @@ import one.profiler.AsyncProfiler;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Collection;
 import java.util.List;
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Predicate;
 
@@ -77,8 +79,8 @@ public class AsyncProfilerJob {
     // Set on init
     /** The platform */
     private SparkPlatform platform;
-    /** The sampling interval in microseconds */
-    private int interval;
+    /** The sample collector */
+    private SampleCollector<?> sampleCollector;
     /** The thread dumper */
     private ThreadDumper threadDumper;
     /** The profiling window */
@@ -100,9 +102,9 @@ public class AsyncProfilerJob {
      * @param command the command
      * @return the output
      */
-    private String execute(String command) {
+    private String execute(Collection<String> command) {
         try {
-            return this.profiler.execute(command);
+            return this.profiler.execute(String.join(",", command));
         } catch (IOException e) {
             throw new RuntimeException("Exception whilst executing profiler command", e);
         }
@@ -118,9 +120,9 @@ public class AsyncProfilerJob {
     }
 
     // Initialise the job
-    public void init(SparkPlatform platform, int interval, ThreadDumper threadDumper, int window, boolean quiet) {
+    public void init(SparkPlatform platform, SampleCollector<?> collector, ThreadDumper threadDumper, int window, boolean quiet) {
         this.platform = platform;
-        this.interval = interval;
+        this.sampleCollector = collector;
         this.threadDumper = threadDumper;
         this.window = window;
         this.quiet = quiet;
@@ -141,16 +143,20 @@ public class AsyncProfilerJob {
             }
 
             // construct a command to send to async-profiler
-            String command = "start,event=" + this.access.getProfilingEvent() + ",interval=" + this.interval + "us,threads,jfr,file=" + this.outputFile.toString();
+            ImmutableList.Builder<String> command = ImmutableList.<String>builder()
+                    .add("start")
+                    .addAll(this.sampleCollector.initArguments(this.access))
+                    .add("threads").add("jfr").add("file=" + this.outputFile.toString());
+
             if (this.quiet) {
-                command += ",loglevel=NONE";
+                command.add("loglevel=NONE");
             }
             if (this.threadDumper instanceof ThreadDumper.Specific) {
-                command += ",filter";
+                command.add("filter");
             }
 
             // start the profiler
-            String resp = execute(command).trim();
+            String resp = execute(command.build()).trim();
 
             if (!resp.equalsIgnoreCase("profiling started")) {
                 throw new RuntimeException("Unexpected response: " + resp);
@@ -208,7 +214,7 @@ public class AsyncProfilerJob {
 
         // read the jfr file produced by async-profiler
         try (JfrReader reader = new JfrReader(this.outputFile)) {
-            readSegments(reader, threadFilter, dataAggregator, this.window);
+            readSegments(reader, this.sampleCollector, threadFilter, dataAggregator);
         } catch (Exception e) {
             boolean fileExists;
             try {
@@ -235,22 +241,9 @@ public class AsyncProfilerJob {
         }
     }
 
-    private void readSegments(JfrReader reader, Predicate<String> threadFilter, AsyncDataAggregator dataAggregator, int window) throws IOException {
-        List<JfrReader.ExecutionSample> samples = reader.readAllEvents(JfrReader.ExecutionSample.class);
-        for (int i = 0; i < samples.size(); i++) {
-            JfrReader.ExecutionSample sample = samples.get(i);
-
-            long duration;
-            if (i == 0) {
-                // we don't really know the duration of the first sample, so just use the sampling
-                // interval
-                duration = this.interval;
-            } else {
-                // calculate the duration of the sample by calculating the time elapsed since the
-                // previous sample
-                duration = TimeUnit.NANOSECONDS.toMicros(sample.time - samples.get(i - 1).time);
-            }
-
+    private <E extends JfrReader.Event> void readSegments(JfrReader reader, SampleCollector<E> collector, Predicate<String> threadFilter, AsyncDataAggregator dataAggregator) throws IOException {
+        List<E> samples = reader.readAllEvents(collector.eventClass());
+        for (E sample : samples) {
             String threadName = reader.threads.get((long) sample.tid);
             if (threadName == null) {
                 continue;
@@ -260,9 +253,11 @@ public class AsyncProfilerJob {
                 continue;
             }
 
+            long value = collector.measure(sample);
+
             // parse the segment and give it to the data aggregator
-            ProfileSegment segment = ProfileSegment.parseSegment(reader, sample, threadName, duration);
-            dataAggregator.insertData(segment, window);
+            ProfileSegment segment = ProfileSegment.parseSegment(reader, sample, threadName, value);
+            dataAggregator.insertData(segment, this.window);
         }
     }
 
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncSampler.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncSampler.java
index 178f055..2328582 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncSampler.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/AsyncSampler.java
@@ -25,6 +25,7 @@ import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import me.lucko.spark.common.SparkPlatform;
 import me.lucko.spark.common.command.sender.CommandSender;
 import me.lucko.spark.common.sampler.AbstractSampler;
+import me.lucko.spark.common.sampler.SamplerMode;
 import me.lucko.spark.common.sampler.SamplerSettings;
 import me.lucko.spark.common.sampler.node.MergeMode;
 import me.lucko.spark.common.sampler.source.ClassSourceLookup;
@@ -41,6 +42,11 @@ import java.util.function.IntPredicate;
  * A sampler implementation using async-profiler.
  */
 public class AsyncSampler extends AbstractSampler {
+
+    /** Function to collect and measure samples - either execution or allocation */
+    private final SampleCollector<?> sampleCollector;
+
+    /** Object that provides access to the async-profiler API */
     private final AsyncProfilerAccess profilerAccess;
 
     /** Responsible for aggregating and then outputting collected sampling data */
@@ -55,8 +61,9 @@ public class AsyncSampler extends AbstractSampler {
     /** The executor used for scheduling and management */
     private ScheduledExecutorService scheduler;
 
-    public AsyncSampler(SparkPlatform platform, SamplerSettings settings) {
+    public AsyncSampler(SparkPlatform platform, SamplerSettings settings, SampleCollector<?> collector) {
         super(platform, settings);
+        this.sampleCollector = collector;
         this.profilerAccess = AsyncProfilerAccess.getInstance(platform);
         this.dataAggregator = new AsyncDataAggregator(settings.threadGrouper());
         this.scheduler = Executors.newSingleThreadScheduledExecutor(
@@ -79,17 +86,21 @@ public class AsyncSampler extends AbstractSampler {
         int window = ProfilingWindowUtils.windowNow();
 
         AsyncProfilerJob job = this.profilerAccess.startNewProfilerJob();
-        job.init(this.platform, this.interval, this.threadDumper, window, this.background);
+        job.init(this.platform, this.sampleCollector, this.threadDumper, window, this.background);
         job.start();
+        this.windowStatisticsCollector.recordWindowStartTime(window);
         this.currentJob = job;
 
         // rotate the sampler job to put data into a new window
-        this.scheduler.scheduleAtFixedRate(
-                this::rotateProfilerJob,
-                ProfilingWindowUtils.WINDOW_SIZE_SECONDS,
-                ProfilingWindowUtils.WINDOW_SIZE_SECONDS,
-                TimeUnit.SECONDS
-        );
+        boolean shouldNotRotate = this.sampleCollector instanceof SampleCollector.Allocation && ((SampleCollector.Allocation) this.sampleCollector).isLiveOnly();
+        if (!shouldNotRotate) {
+            this.scheduler.scheduleAtFixedRate(
+                    this::rotateProfilerJob,
+                    ProfilingWindowUtils.WINDOW_SIZE_SECONDS,
+                    ProfilingWindowUtils.WINDOW_SIZE_SECONDS,
+                    TimeUnit.SECONDS
+            );
+        }
 
         recordInitialGcStats();
         scheduleTimeout();
@@ -106,9 +117,6 @@ public class AsyncSampler extends AbstractSampler {
                 try {
                     // stop the previous job
                     previousJob.stop();
-
-                    // collect statistics for the window
-                    this.windowStatisticsCollector.measureNow(previousJob.getWindow());
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
@@ -116,10 +124,18 @@ public class AsyncSampler extends AbstractSampler {
                 // start a new job
                 int window = previousJob.getWindow() + 1;
                 AsyncProfilerJob newJob = this.profilerAccess.startNewProfilerJob();
-                newJob.init(this.platform, this.interval, this.threadDumper, window, this.background);
+                newJob.init(this.platform, this.sampleCollector, this.threadDumper, window, this.background);
                 newJob.start();
+                this.windowStatisticsCollector.recordWindowStartTime(window);
                 this.currentJob = newJob;
 
+                // collect statistics for the previous window
+                try {
+                    this.windowStatisticsCollector.measureNow(previousJob.getWindow());
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+
                 // aggregate the output of the previous job
                 previousJob.aggregate(this.dataAggregator);
 
@@ -174,6 +190,11 @@ public class AsyncSampler extends AbstractSampler {
     }
 
     @Override
+    public SamplerMode getMode() {
+        return this.sampleCollector.getMode();
+    }
+
+    @Override
     public SamplerData toProto(SparkPlatform platform, CommandSender creator, String comment, MergeMode mergeMode, ClassSourceLookup classSourceLookup) {
         SamplerData.Builder proto = SamplerData.newBuilder();
         writeMetadataToProto(proto, platform, creator, comment, this.dataAggregator);
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/ProfileSegment.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/ProfileSegment.java
index 26debaf..0804ccf 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/ProfileSegment.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/ProfileSegment.java
@@ -38,13 +38,13 @@ public class ProfileSegment {
     /** The stack trace for this segment */
     private final AsyncStackTraceElement[] stackTrace;
     /** The time spent executing this segment in microseconds */
-    private final long time;
+    private final long value;
 
-    public ProfileSegment(int nativeThreadId, String threadName, AsyncStackTraceElement[] stackTrace, long time) {
+    public ProfileSegment(int nativeThreadId, String threadName, AsyncStackTraceElement[] stackTrace, long value) {
         this.nativeThreadId = nativeThreadId;
         this.threadName = threadName;
         this.stackTrace = stackTrace;
-        this.time = time;
+        this.value = value;
     }
 
     public int getNativeThreadId() {
@@ -59,11 +59,11 @@ public class ProfileSegment {
         return this.stackTrace;
     }
 
-    public long getTime() {
-        return this.time;
+    public long getValue() {
+        return this.value;
     }
 
-    public static ProfileSegment parseSegment(JfrReader reader, JfrReader.ExecutionSample sample, String threadName, long duration) {
+    public static ProfileSegment parseSegment(JfrReader reader, JfrReader.Event sample, String threadName, long value) {
         JfrReader.StackTrace stackTrace = reader.stackTraces.get(sample.stackTraceId);
         int len = stackTrace.methods.length;
 
@@ -72,7 +72,7 @@ public class ProfileSegment {
             stack[i] = parseStackFrame(reader, stackTrace.methods[i]);
         }
 
-        return new ProfileSegment(sample.tid, threadName, stack, duration);
+        return new ProfileSegment(sample.tid, threadName, stack, value);
     }
 
     private static AsyncStackTraceElement parseStackFrame(JfrReader reader, long methodId) {
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/async/SampleCollector.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/SampleCollector.java
new file mode 100644
index 0000000..6054b91
--- /dev/null
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/async/SampleCollector.java
@@ -0,0 +1,154 @@
+/*
+ * This file is part of spark.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package me.lucko.spark.common.sampler.async;
+
+import com.google.common.collect.ImmutableList;
+
+import me.lucko.spark.common.sampler.SamplerMode;
+import me.lucko.spark.common.sampler.async.AsyncProfilerAccess.ProfilingEvent;
+import me.lucko.spark.common.sampler.async.jfr.JfrReader.AllocationSample;
+import me.lucko.spark.common.sampler.async.jfr.JfrReader.Event;
+import me.lucko.spark.common.sampler.async.jfr.JfrReader.ExecutionSample;
+
+import java.util.Collection;
+import java.util.Objects;
+
+/**
+ * Collects and processes sample events for a given type.
+ *
+ * @param <E> the event type
+ */
+public interface SampleCollector<E extends Event> {
+
+    /**
+     * Gets the arguments to initialise the profiler.
+     *
+     * @param access the async profiler access object
+     * @return the initialisation arguments
+     */
+    Collection<String> initArguments(AsyncProfilerAccess access);
+
+    /**
+     * Gets the event class processed by this sample collector.
+     *
+     * @return the event class
+     */
+    Class<E> eventClass();
+
+    /**
+     * Gets the measurements for a given event
+     *
+     * @param event the event
+     * @return the measurement
+     */
+    long measure(E event);
+
+    /**
+     * Gets the mode for the collector.
+     *
+     * @return the mode
+     */
+    SamplerMode getMode();
+
+    /**
+     * Sample collector for execution (cpu time) profiles.
+     */
+    final class Execution implements SampleCollector<ExecutionSample> {
+        private final int interval; // time in microseconds
+
+        public Execution(int interval) {
+            this.interval = interval;
+        }
+
+        @Override
+        public Collection<String> initArguments(AsyncProfilerAccess access) {
+            ProfilingEvent event = access.getProfilingEvent();
+            Objects.requireNonNull(event, "event");
+
+            return ImmutableList.of(
+                    "event=" + event,
+                    "interval=" + this.interval + "us"
+            );
+        }
+
+        @Override
+        public Class<ExecutionSample> eventClass() {
+            return ExecutionSample.class;
+        }
+
+        @Override
+        public long measure(ExecutionSample event) {
+            return event.value() * this.interval;
+        }
+
+        @Override
+        public SamplerMode getMode() {
+            return SamplerMode.EXECUTION;
+        }
+    }
+
+    /**
+     * Sample collector for allocation (memory) profiles.
+     */
+    final class Allocation implements SampleCollector<AllocationSample> {
+        private final int intervalBytes;
+        private final boolean liveOnly;
+
+        public Allocation(int intervalBytes, boolean liveOnly) {
+            this.intervalBytes = intervalBytes;
+            this.liveOnly = liveOnly;
+        }
+
+        public boolean isLiveOnly() {
+            return this.liveOnly;
+        }
+
+        @Override
+        public Collection<String> initArguments(AsyncProfilerAccess access) {
+            ProfilingEvent event = access.getAllocationProfilingEvent();
+            Objects.requireNonNull(event, "event");
+
+            ImmutableList.Builder<String> builder = ImmutableList.builder();
+            builder.add("event=" + event);
+            builder.add("alloc=" + this.intervalBytes);
+            if (this.liveOnly) {
+                builder.add("live");
+            }
+            return builder.build();
+        }
+
+        @Override
+        public Class<AllocationSample> eventClass() {
+            return AllocationSample.class;
+        }
+
+        @Override
+        public long measure(AllocationSample event) {
+            return event.value();
+        }
+
+        @Override
+        public SamplerMode getMode() {
+            return SamplerMode.ALLOCATION;
+        }
+    }
+
+}
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/java/JavaSampler.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/java/JavaSampler.java
index 72a37e8..d5c965f 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/java/JavaSampler.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/java/JavaSampler.java
@@ -25,6 +25,7 @@ import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import me.lucko.spark.common.SparkPlatform;
 import me.lucko.spark.common.command.sender.CommandSender;
 import me.lucko.spark.common.sampler.AbstractSampler;
+import me.lucko.spark.common.sampler.SamplerMode;
 import me.lucko.spark.common.sampler.SamplerSettings;
 import me.lucko.spark.common.sampler.node.MergeMode;
 import me.lucko.spark.common.sampler.source.ClassSourceLookup;
@@ -90,6 +91,7 @@ public class JavaSampler extends AbstractSampler implements Runnable {
             }
         }
 
+        this.windowStatisticsCollector.recordWindowStartTime(ProfilingWindowUtils.unixMillisToWindow(this.startTime));
         this.task = this.workerPool.scheduleAtFixedRate(this, 0, this.interval, TimeUnit.MICROSECONDS);
     }
 
@@ -149,6 +151,9 @@ public class JavaSampler extends AbstractSampler implements Runnable {
             int previousWindow = JavaSampler.this.lastWindow.getAndUpdate(previous -> Math.max(this.window, previous));
             if (previousWindow != 0 && previousWindow != this.window) {
 
+                // record the start time for the new window
+                JavaSampler.this.windowStatisticsCollector.recordWindowStartTime(this.window);
+
                 // collect statistics for the previous window
                 JavaSampler.this.windowStatisticsCollector.measureNow(previousWindow);
 
@@ -168,4 +173,8 @@ public class JavaSampler extends AbstractSampler implements Runnable {
         return proto.build();
     }
 
+    @Override
+    public SamplerMode getMode() {
+        return SamplerMode.EXECUTION;
+    }
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/window/ProtoTimeEncoder.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/window/ProtoTimeEncoder.java
index 03da075..fb4a4fc 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/window/ProtoTimeEncoder.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/window/ProtoTimeEncoder.java
@@ -27,18 +27,25 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.LongAdder;
+import java.util.function.LongToDoubleFunction;
 import java.util.stream.IntStream;
 
 /**
  * Encodes a map of int->double into a double array.
  */
 public class ProtoTimeEncoder {
+
+    /** A transformer function to transform the 'time' value from a long to a double */
+    private final LongToDoubleFunction valueTransformer;
+
     /** A sorted array of all possible keys to encode */
     private final int[] keys;
     /** A map of key value -> index in the keys array */
     private final Map<Integer, Integer> keysToIndex;
 
-    public ProtoTimeEncoder(List<ThreadNode> sourceData) {
+    public ProtoTimeEncoder(LongToDoubleFunction valueTransformer, List<ThreadNode> sourceData) {
+        this.valueTransformer = valueTransformer;
+
         // get an array of all keys that show up in the source data
         this.keys = sourceData.stream()
                 .map(n -> n.getTimeWindows().stream().mapToInt(i -> i))
@@ -81,11 +88,8 @@ public class ProtoTimeEncoder {
                 throw new RuntimeException("No index for key " + key + " in " + this.keysToIndex.keySet());
             }
 
-            // convert the duration from microseconds -> milliseconds
-            double durationInMilliseconds = value.longValue() / 1000d;
-
             // store in the array
-            array[idx] = durationInMilliseconds;
+            array[idx] = this.valueTransformer.applyAsDouble(value.longValue());
         });
 
         return array;
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/window/WindowStatisticsCollector.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/window/WindowStatisticsCollector.java
index ce65013..1c05b00 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/window/WindowStatisticsCollector.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/window/WindowStatisticsCollector.java
@@ -29,20 +29,26 @@ import me.lucko.spark.common.tick.TickHook;
 import me.lucko.spark.common.util.RollingAverage;
 import me.lucko.spark.proto.SparkProtos;
 
+import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.IntPredicate;
+import java.util.logging.Level;
 
 /**
  * Collects statistics for each profiling window.
  */
 public class WindowStatisticsCollector {
-    private static final SparkProtos.WindowStatistics ZERO = SparkProtos.WindowStatistics.newBuilder().build();
+    private static final SparkProtos.WindowStatistics ZERO = SparkProtos.WindowStatistics.newBuilder()
+            .setDuration(ProfilingWindowUtils.WINDOW_SIZE_SECONDS * 1000)
+            .build();
 
     /** The platform */
     private final SparkPlatform platform;
 
+    /** Map of profiling window -> start time */
+    private final Map<Integer, Long> windowStartTimes = new HashMap<>();
     /** Map of profiling window -> statistics */
     private final Map<Integer, SparkProtos.WindowStatistics> stats;
 
@@ -100,12 +106,21 @@ public class WindowStatisticsCollector {
     }
 
     /**
+     * Records the wall-clock time when a window was started.
+     *
+     * @param window the window
+     */
+    public void recordWindowStartTime(int window) {
+        this.windowStartTimes.put(window, System.currentTimeMillis());
+    }
+
+    /**
      * Measures statistics for the given window if none have been recorded yet.
      *
      * @param window the window
      */
     public void measureNow(int window) {
-        this.stats.computeIfAbsent(window, w -> measure());
+        this.stats.computeIfAbsent(window, this::measure);
     }
 
     /**
@@ -132,9 +147,20 @@ public class WindowStatisticsCollector {
      *
      * @return the current statistics
      */
-    private SparkProtos.WindowStatistics measure() {
+    private SparkProtos.WindowStatistics measure(int window) {
         SparkProtos.WindowStatistics.Builder builder = SparkProtos.WindowStatistics.newBuilder();
 
+        long endTime = System.currentTimeMillis();
+        Long startTime = this.windowStartTimes.get(window);
+        if (startTime == null) {
+            this.platform.getPlugin().log(Level.WARNING, "Unknown start time for window " + window);
+            startTime = endTime - (ProfilingWindowUtils.WINDOW_SIZE_SECONDS * 1000); // guess
+        }
+
+        builder.setStartTime(startTime);
+        builder.setEndTime(endTime);
+        builder.setDuration((int) (endTime - startTime));
+
         TickStatistics tickStatistics = this.platform.getTickStatistics();
         if (tickStatistics != null) {
             builder.setTps(tickStatistics.tps1Min());
diff --git a/spark-common/src/main/proto/spark/spark.proto b/spark-common/src/main/proto/spark/spark.proto
index f61e585..2004415 100644
--- a/spark-common/src/main/proto/spark/spark.proto
+++ b/spark-common/src/main/proto/spark/spark.proto
@@ -165,6 +165,11 @@ message WindowStatistics {
   int32 entities = 8;
   int32 tile_entities = 9;
   int32 chunks = 10;
+
+  // approximate wall-clock start/end times
+  int64 start_time = 11;
+  int64 end_time = 12;
+  int32 duration = 13;
 }
 
 message RollingAverageValues {
diff --git a/spark-common/src/main/proto/spark/spark_sampler.proto b/spark-common/src/main/proto/spark/spark_sampler.proto
index 245da37..60cffac 100644
--- a/spark-common/src/main/proto/spark/spark_sampler.proto
+++ b/spark-common/src/main/proto/spark/spark_sampler.proto
@@ -32,6 +32,7 @@ message SamplerMetadata {
   int32 number_of_ticks = 12;
   map<string, SourceMetadata> sources = 13;
   map<string, string> extra_platform_metadata = 14;
+  SamplerMode sampler_mode = 15;
 
   message ThreadDumper {
     Type type = 1;
@@ -67,6 +68,11 @@ message SamplerMetadata {
     string name = 1;
     string version = 2;
   }
+
+  enum SamplerMode {
+    EXECUTION = 0;
+    ALLOCATION = 1;
+  }
 }
 
 message ThreadNode {