statement-store: do_propagate_statements takes unusual long time

[alexggh]

Notice do_propagate_statements takes in the oder of seconds, when dealing with a lot of statements (100k)

Do propagate took 4377 ms
Do propagate took 4998 ms
Do propagate took 4703 ms

This is bad for a few reasons:

1. It slows the propagation to other peers.
2. It keeps the main loop busy for this amount of time.

The main culprit for this is this line of code:

polkadot-sdk/substrate/client/network/statement/src/lib.rs

Line 597 in 0241d9b

let encoded_size = chunk.encoded_size();

, which repeatedly encodes all statements after each chunk send.

The fix is to pick a chunk size, so that on the hot path, we don't have repeatedly encode all statements we want send in a loop.

[Stephenlawrence00]

@alexggh Can I take a look into this?

[P1sar]

@Stephenlawrence00 Thanks for the suggestion. Since this is fairly time-sensitive, we’ll take care of it on our end.