Add support for displaying extra IPC markers (PR #2535)

docs-user/_sidebar.md

@@ -9,6 +9,7 @@
   * [Remote profiling on Android](./guide-remote-profiling.md)
   * [Perf profiling on Linux](./guide-perf-profiling.md)
   * [Memory Allocations](./memory-allocations.md)
+  * [IPC Messages](./ipc-messages.md)
 * [Video Tutorials](./videos.md)
   * [Firefox Profiler intro](./videos-intro.md)
   * [Samples and markers](./videos-samples-markers.md)

docs-user/ipc-messages.md

@@ -0,0 +1,44 @@
+# IPC Messages
+
+The Firefox Profiler supports recording IPC messages for any actively-profiled
+thread. During profiling, each IPC message is recorded with 5 events:
+
+1. When the `SendXXX` function is called on the origin thread
+2. When the sender's IO thread begins sending bytes over the IPC channel
+3. When the sender's IO thread finishes sending bytes over the IPC channel
+4. When the recipient's IO thread finishes receiving bytes from the IPC channel
+5. When the `RecvXXX` function is called on the destination thread
+
+## IPC Track
+
+After collecting a profile with IPC messages, there will be a new track in the
+timeline showing the outgoing (blue) and incoming (purple) IPC messages.
+Hovering over a marker for an IPC message will provide more details about it:
+
+![A screenshot of the popup UI for an IPC message.](images/ipc-messages-popup.png)
+
+Each IPC message has several durations associated with it, corresponding to the
+spans of time between consecutive IPC message phases as described above:
+
+* *Send thread latency*: the time between `SendXXX` being called and the first
+  byte sent over the IPC channel
+* *IPC send duration*: the time taken to send all the bytes over the IPC channel
+* *IPC recv latency*: the time between the last byte being sent over the IPC
+  channel and the last byte being *received*
+* *Recv thread latency*: the time between the last byte being received from the
+  IPC channel and the `RecvXXX` function being called
+
+## Enabling the Feature
+
+In `about:profiling`, scroll down to the `Features` section and enable the
+`IPC Messages` checkbox.
+
+![A screenshot of the UI to turn on IPC messages.](images/ipc-messages-feature.png)
+
+### Profiling the IO Threads
+
+By default, the sender's and recipient's IO threads aren't included in a
+profile. To include these, add `Gecko_IOThread` and  `Chrome_ChildThread` to the
+list of threads to be profiled.
+
+![A screenshot of the UI to profile the IO threads](images/ipc-messages-io-threads.png)

src/components/tooltip/Marker.js

@@ -197,6 +197,16 @@ function _sumMaybeEntries(
     .reduce((a, x) => a + x, 0);
 }
 
+function _maybeFormatDuration(
+  start: number | void,
+  end: number | void
+): string {
+  if (start !== undefined && end !== undefined) {
+    return formatMilliseconds(end - start);
+  }
+  return 'unknown';
+}
+
 const MaybeBacktrace = ({
   marker,
   thread,
@@ -635,6 +645,18 @@ function getMarkerDetails(
           <TooltipDetails>
             <TooltipDetail label="Type">{data.messageType}</TooltipDetail>
             <TooltipDetail label="Sync">{data.sync.toString()}</TooltipDetail>
+            <TooltipDetail label="Send Thread Latency">
+              {_maybeFormatDuration(data.startTime, data.sendStartTime)}
+            </TooltipDetail>
+            <TooltipDetail label="IPC Speed">
+              {_maybeFormatDuration(data.sendStartTime, data.sendEndTime)}
+            </TooltipDetail>
+            <TooltipDetail label="IPC Latency">
+              {_maybeFormatDuration(data.sendEndTime, data.recvEndTime)}
+            </TooltipDetail>
+            <TooltipDetail label="Recv Thread Latency">
+              {_maybeFormatDuration(data.recvEndTime, data.endTime)}
+            </TooltipDetail>
           </TooltipDetails>
         );
         break;