Add profiling support to memscope

Author: stevegolton

ui/src/plugins/dev.perfetto.Memscope/components/progress_bar.scss

@@ -0,0 +1,51 @@
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+.pf-progress {
+  display: grid;
+  grid-template-columns: auto 1fr auto;
+  align-items: center;
+  gap: 10px;
+  font-size: var(--pf-font-size-s);
+  color: var(--pf-color-text-muted);
+}
+
+.pf-progress__label {
+  font-weight: 600;
+}
+
+.pf-progress__track {
+  height: 6px;
+  border-radius: 3px;
+  background: var(--pf-color-background);
+  overflow: hidden;
+}
+
+.pf-progress__fill {
+  height: 100%;
+  background: var(--pf-color-primary);
+  transition: width 0.3s ease;
+}
+
+.pf-progress__value {
+  font-variant-numeric: tabular-nums;
+  font-weight: 600;
+  color: var(--pf-color-text);
+  white-space: nowrap;
+}
+
+.pf-progress__suffix {
+  color: var(--pf-color-text-muted);
+  font-weight: 400;
+}

ui/src/plugins/dev.perfetto.Memscope/components/progress_bar.ts

@@ -0,0 +1,48 @@
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import m from 'mithril';
+import {clamp} from '../../../base/math_utils';
+
+export interface ProgressBarAttrs {
+  // Percentage 0..100. Values outside the range are clamped.
+  readonly pct: number;
+  // Optional label shown to the left of the track.
+  readonly label?: m.Children;
+  // Optional value shown to the right. If omitted, "<pct>%" is shown.
+  readonly value?: m.Children;
+  // Optional muted suffix appended after the value (e.g. " / 640 MB").
+  readonly suffix?: m.Children;
+}
+
+export class ProgressBar implements m.ClassComponent<ProgressBarAttrs> {
+  view({attrs}: m.Vnode<ProgressBarAttrs>) {
+    const clamped = clamp(attrs.pct, 0, 100);
+    const value = attrs.value ?? `${clamped.toFixed(1)}%`;
+    return m(
+      '.pf-progress',
+      attrs.label !== undefined && m('.pf-progress__label', attrs.label),
+      m(
+        '.pf-progress__track',
+        m('.pf-progress__fill', {style: {width: `${clamped}%`}}),
+      ),
+      m(
+        '.pf-progress__value',
+        value,
+        attrs.suffix !== undefined &&
+          m('span.pf-progress__suffix', attrs.suffix),
+      ),
+    );
+  }
+}

ui/src/plugins/dev.perfetto.Memscope/index.ts

@@ -52,7 +52,7 @@ export default class implements PerfettoPlugin {
         } else {
           return m(ConnectionPage, {
             onConnected: (result) => {
-              session = new LiveSession(result);
+              session = new LiveSession(app, result);
               session.onSnapshot(() => m.redraw());
             },
           });

ui/src/plugins/dev.perfetto.Memscope/sessions/live_session.ts

@@ -21,7 +21,18 @@ import {AdbDevice} from '../../dev.perfetto.RecordTraceV2/adb/adb_device';
 import {createAdbTracingSession} from '../../dev.perfetto.RecordTraceV2/adb/adb_tracing_session';
 import {TracingSession} from '../../dev.perfetto.RecordTraceV2/interfaces/tracing_session';
 import {TracedWebsocketTarget} from '../../dev.perfetto.RecordTraceV2/traced_over_websocket/traced_websocket_target';
+import {App} from '../../../public/app';
 import {ConnectionResult} from '../views/connection';
+import {ProfileSession, type ProfileState} from './profile_session';
+
+export interface ProfileView {
+  readonly pid: number;
+  readonly processName: string;
+  readonly state: ProfileState;
+  readonly bufferUsagePct?: number;
+  /** Wall-clock timestamp (ms) at which profiling started. */
+  readonly startMs: number;
+}
 
 const SNAPSHOT_INTERVAL_MS = 3_000; // How over to take a snapshot of the runnign trace and extract data.
 const INITIAL_SNAPSHOT_INTERVAL_MS = 1_000; // Use a shorter interval for the first snapshot to get data on screen faster.
@@ -83,6 +94,7 @@ export type OnSnapshotCallback = (data: SnapshotData) => void;
  * notifies registered callbacks.
  */
 export class LiveSession {
+  private readonly app: App;
   private session?: TracingSession;
   private engine?: WasmEngineProxy;
   private readonly sessionName: string;
@@ -113,7 +125,23 @@ export class LiveSession {
   // True when the last snapshot took longer than the configured interval.
   snapshotOverrun = false;
 
-  constructor(conn: ConnectionResult) {
+  // Active process profile (if any). Undefined when no profile is running.
+  private profileImpl?: {session: ProfileSession; startMs: number};
+
+  get profile(): ProfileView | undefined {
+    const p = this.profileImpl;
+    if (p === undefined) return undefined;
+    return {
+      pid: p.session.pid,
+      processName: p.session.processName,
+      state: p.session.state,
+      bufferUsagePct: p.session.bufferUsagePct,
+      startMs: p.startMs,
+    };
+  }
+
+  constructor(app: App, conn: ConnectionResult) {
+    this.app = app;
     this.device = conn.device;
     this.linuxTarget = conn.linuxTarget;
     this.deviceName = conn.deviceName;
@@ -151,6 +179,43 @@ export class LiveSession {
     }
   }
 
+  /** Starts a heap profiling session for a single process. */
+  async startProfile(pid: number, processName: string): Promise<void> {
+    if (this.profileImpl) {
+      await this.profileImpl.session.cancel();
+    }
+    const session = await ProfileSession.start(
+      this.linuxTarget ?? this.device!,
+      pid,
+      processName,
+      this.data?.xMax ?? 0,
+    );
+    this.profileImpl = {session, startMs: Date.now()};
+  }
+
+  /** Stops the active profile and opens the trace in the main UI. */
+  async stopAndOpenProfile(): Promise<void> {
+    const profile = this.profileImpl?.session;
+    if (!profile) return;
+    const processName = profile.processName;
+    const pid = profile.pid;
+    await profile.stop();
+    const traceData = profile.getTraceData();
+    this.profileImpl = undefined;
+    if (traceData) {
+      const fileName = `heap-${processName}-${pid}.perfetto-trace`;
+      const buffer = traceData.buffer as ArrayBuffer;
+      this.app.openTraceFromBuffer({buffer, title: fileName, fileName});
+    }
+  }
+
+  /** Cancels the active profile and discards data. */
+  async cancelProfile(): Promise<void> {
+    if (!this.profileImpl) return;
+    await this.profileImpl.session.cancel();
+    this.profileImpl = undefined;
+  }
+
   /** Stops the tracing session, polling, and disposes of the engine. */
   async dispose(): Promise<void> {
     // Mark disposed first so any in-flight poll() bails out before touching

ui/src/plugins/dev.perfetto.Memscope/sessions/profile_session.ts

@@ -0,0 +1,188 @@
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import protos from '../../../protos';
+import {AdbDevice} from '../../dev.perfetto.RecordTraceV2/adb/adb_device';
+import {createAdbTracingSession} from '../../dev.perfetto.RecordTraceV2/adb/adb_tracing_session';
+import {TracingSession} from '../../dev.perfetto.RecordTraceV2/interfaces/tracing_session';
+import {TracedWebsocketTarget} from '../../dev.perfetto.RecordTraceV2/traced_over_websocket/traced_websocket_target';
+
+const DUMP_INTERVAL_MS = 10_000;
+const PROC_STATS_BUFFER_SIZE_KB = 4 * 1024;
+const HEAPPROFD_BUFFER_SIZE_KB = 128 * 1024;
+const JAVA_HPROF_BUFFER_SIZE_KB = 256 * 1024;
+const STATS_POLL_INTERVAL_MS = 3000;
+
+export type ProfileState = 'recording' | 'stopping' | 'finished' | 'error';
+
+export class ProfileSession {
+  readonly pid: number;
+  readonly processName: string;
+  readonly startX: number;
+
+  private inner?: TracingSession;
+  private intervalHandle?: ReturnType<typeof setInterval>;
+  private _state: ProfileState = 'recording';
+  private _error?: string;
+  private _bufferUsagePct?: number;
+
+  private constructor(pid: number, processName: string, startX: number) {
+    this.pid = pid;
+    this.processName = processName;
+    this.startX = startX;
+  }
+
+  static async start(
+    targetOrDevice: TracedWebsocketTarget | AdbDevice,
+    pid: number,
+    processName: string,
+    startX: number,
+  ): Promise<ProfileSession> {
+    const self = new ProfileSession(pid, processName, startX);
+    const config = buildProcessProfileConfig(pid);
+    const result =
+      targetOrDevice instanceof TracedWebsocketTarget
+        ? await targetOrDevice.startTracing(config)
+        : await createAdbTracingSession(targetOrDevice, config);
+    if (!result.ok) {
+      self._state = 'error';
+      self._error = `Failed to start profile: ${result.error}`;
+      return self;
+    }
+    self.inner = result.value;
+    self.intervalHandle = setInterval(async () => {
+      self._bufferUsagePct = await self.inner!.getBufferUsagePct();
+    }, STATS_POLL_INTERVAL_MS);
+    self.inner.onSessionUpdate.addListener(() => {
+      const s = self.inner!.state;
+      if (s === 'FINISHED') {
+        self._state = 'finished';
+      } else if (s === 'ERRORED') {
+        self._state = 'error';
+        self._error = self
+          .inner!.logs.filter((l) => l.isError)
+          .map((l) => l.message)
+          .join('; ');
+      }
+    });
+    return self;
+  }
+
+  get state(): ProfileState {
+    return this._state;
+  }
+
+  get error(): string | undefined {
+    return this._error;
+  }
+
+  get bufferUsagePct(): number | undefined {
+    return this._bufferUsagePct;
+  }
+
+  /** Stops recording and waits for the trace data to be ready. */
+  async stop(): Promise<void> {
+    if (this._state !== 'recording' || this.inner === undefined) return;
+    clearInterval(this.intervalHandle);
+    this._state = 'stopping';
+    await this.inner.stop();
+    if (this.inner.state !== 'FINISHED') {
+      await new Promise<void>((resolve) => {
+        const sub = this.inner!.onSessionUpdate.addListener(() => {
+          const s = this.inner!.state;
+          if (s === 'FINISHED' || s === 'ERRORED') {
+            sub[Symbol.dispose]();
+            resolve();
+          }
+        });
+      });
+    }
+    this._state = this.inner.state === 'FINISHED' ? 'finished' : 'error';
+  }
+
+  /** Cancels recording and discards trace data. */
+  async cancel(): Promise<void> {
+    if (this._state !== 'recording' || this.inner === undefined) return;
+    clearInterval(this.intervalHandle);
+    this._state = 'error';
+    await this.inner.cancel();
+  }
+
+  /** Returns the trace buffer once state is 'finished'. */
+  getTraceData(): Uint8Array | undefined {
+    return this.inner?.getTraceData();
+  }
+}
+
+function buildProcessProfileConfig(pid: number): protos.ITraceConfig {
+  return {
+    compressionType:
+      protos.TraceConfig.CompressionType.COMPRESSION_TYPE_DEFLATE,
+    buffers: [
+      {
+        name: 'process_stats',
+        sizeKb: PROC_STATS_BUFFER_SIZE_KB,
+        fillPolicy: protos.TraceConfig.BufferConfig.FillPolicy.DISCARD,
+      },
+      {
+        name: 'heapprofd',
+        sizeKb: HEAPPROFD_BUFFER_SIZE_KB,
+        fillPolicy: protos.TraceConfig.BufferConfig.FillPolicy.RING_BUFFER,
+      },
+      {
+        name: 'java_hprof',
+        sizeKb: JAVA_HPROF_BUFFER_SIZE_KB,
+        fillPolicy: protos.TraceConfig.BufferConfig.FillPolicy.RING_BUFFER,
+      },
+    ],
+    dataSources: [
+      {
+        config: {
+          name: 'linux.process_stats',
+          targetBufferName: 'process_stats',
+          processStatsConfig: {
+            scanAllProcessesOnStart: true, // Necessary for track names.
+          },
+        },
+      },
+      {
+        config: {
+          name: 'android.heapprofd',
+          targetBufferName: 'heapprofd',
+          heapprofdConfig: {
+            pid: [pid],
+            samplingIntervalBytes: 32 * 1024, // Slightly larger than default to reduce overhead.
+            shmemSizeBytes: 16 * 1024 * 1024, // Arbitrary, could use default.
+            blockClient: true, // Important for trace integrity.
+            continuousDumpConfig: {
+              dumpIntervalMs: DUMP_INTERVAL_MS, // Important for getting regular heap snapshots to see how memory usage evolves over time.
+            },
+          },
+        },
+      },
+      {
+        config: {
+          name: 'android.java_hprof',
+          targetBufferName: 'java_hprof',
+          javaHprofConfig: {
+            pid: [pid],
+            continuousDumpConfig: {
+              dumpIntervalMs: DUMP_INTERVAL_MS, // Required for Java profiles.
+            },
+          },
+        },
+      },
+    ],
+  };
+}