Batch BLS verification for attestations

[dapplion]

Is your feature request related to a problem? Please describe.

Very promising optimization, it has been very successful in Nimbus and Lighthouse. See results here: https://github.com/sigp/lighthouse/pull/2399. We struggle to process all attestations and aggregates in Prater, this will help a lot.

Describe the solution you'd like

https://github.com/sigp/lighthouse/pull/2399

[g11tech]

@dapplion kindly assign, could take a look at it and study lighthouse implementation while crunching metrics

[dapplion]

Taking it myself since it's time-sensitive. I do recommend to take in less wide reaching complex tasks just to get a better handle on the lodestar package, gossip, etc.

[dapplion]

After thinking about it for while the best to put this is in the BLS queue itself.

• Buffer submitted work for some time (~10-100ms)
• Then construct packets of work that will be verified in batch, if some re-verify all individually. This logic should happen in the worker side to reduce communication.
• We can add logic to only allow this behaviour on certain work packets.
• The BLS queue should not apply this strategy to work with a lot a signature sets, only to those with fewer than 3-5 (aggregates + attesations)

Still WIP: How to efficiently force buffering without slowing processing when it's necessary? I.e. we don't want to slow syncing or block processing.

• Def we should only buffer objects that request than. The gossip att and agg functions should pass a flag to the bls verifier
• The BLS verifier can have two arrays (a, b) where it places objects depending on the current time.

  
  onWork(work) {
  if (work.shouldBuffer) {
  if (now % 100 < 50) {
    a.push(work)
  } else {
    b.push(work)
  }
  } else {
  submitWork(work)
  }
  }

when(now % 100 === 0, () => submitWork(a)) when(now % 100 === 50, () => submitWork(b))