avoid round trip in smart wallet vstorage / storageNode writes

[dckc]

What is the Problem Being Solved?

While looking at performance of a PSM trade (#6039), we noticed two round trips in each wallet state update - one for serialize and one for setValue:

I re-discovered this pattern in

• spike for load testing Fast USDC #10231

Description of the Design

Have the board marshaller return JSON.stringify(capData) rather than capData. Then the smart wallet can do

  const stringValueP = E(boardMarshaller).serializeAndStringify(objectGraph);
  await E(storageNode).setValue(stringValueP);

and stringValueP can be forwarded to the bridge vat without a round trip back thru the smart wallet.

There's a proof of concept in...

• feat: integrate JSON.stringify/parse in board marshallers #6646

Security Considerations

Scaling Considerations

fewer round trips should scale better

Test Plan

• how to verify in a test that we avoided the round trip??

Upgrade Considerations

This would be deployed in an upgrade of walletFactory.

It would be nice to update any other clients that exhibit this pattern, but this issue is scoped to the smart wallet, which is where we see the problem happen most often.

[gibson042]

We could also enhance the StorageNode API to perform serialization locally:

  const capDataP = E(boardMarshaller).toCapData(objectGraph);
  await E(storageNode).serializeAndSetValue(capDataP);

(which would likely have smaller overall message size by avoiding the double encoding necessary to send an already serialized representation, but may be more difficult to effect because it would require upgrading the bridge vat)