diff --git a/packages/SwingSet/src/controller/startNodeSubprocess.js b/packages/SwingSet/src/controller/startNodeSubprocess.js
index a392b94944d..72ff6095fdb 100644
--- a/packages/SwingSet/src/controller/startNodeSubprocess.js
+++ b/packages/SwingSet/src/controller/startNodeSubprocess.js
@@ -13,6 +13,12 @@ export function makeStartSubprocessWorkerNode(
     ).pathname;
     const args = nodeOptions ? [...nodeOptions] : [];
     if (profileVats.includes(vatID)) {
+      // Enable profiling with a 1 microsecond sampling interval,
+      // saving results to a file in the working directory
+      // with a portable name derived from the vat name
+      // and in particular replacing any colons with dashes.
+      // cf. ../kernel/vat-loader/manager-subprocess-node.js
+      // https://github.com/Agoric/agoric-sdk/blob/18d561f1b95755e58ca691b26938fc249618018d/packages/SwingSet/src/kernel/vat-loader/manager-subprocess-node.js#L32-L34
       args.push('--cpu-prof');
       args.push('--cpu-prof-interval');
       args.push('1');