Too many closures retained in heap memory

[twoeths]

Describe the bug

When I run benchmark for processInactivityUpdates I found that there are too many closures retained

Most of them are from the hook when we get sub tree

Expected behavior

• Since the hook is important to update the parent tree, I'd think if it's possible to create getSubTreeReadonly to avoid the hook? That should work for some use cases.
• Find and avoid the below pattern to avoid accessing a property inside state too frequently

for (let i = 0; i < process.statuses.length; i++) {
    const status = process.statuses[i];
    if (hasMarkers(status.flags, FLAG_ELIGIBLE_ATTESTER)) {
      if (hasMarkers(status.flags, FLAG_PREV_TARGET_ATTESTER_OR_UNSLASHED)) {
        state.inactivityScores[i] -= Math.min(1, state.inactivityScores[i]);
      } else {
        state.inactivityScores[i] += Number(INACTIVITY_SCORE_BIAS);
      }
      if (!inActivityLeak) {
        state.inactivityScores[i] -= Math.min(Number(INACTIVITY_SCORE_RECOVERY_RATE), state.inactivityScores[i]);
      }
    }
  }

in the example above, we should get state.inactivityScores only 1 time and assign to a separate variable.
How to reproduce
Run processInactivityUpdates benchmark

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 15 days if no further activity occurs. Thank you for your contributions.

[dapplion]

@tuyennhv Once we merge all the memory related improvements we should do another round of heap snapshots to validate the improvements. Then we can review this issues 👍

[dapplion]

Bump

[dapplion]

@tuyennhv Would be nice get a heap snapshot of latest version and compare. With recent ssz bump there's should be no more closures for to tree hooks

[dapplion]

Closing issues for specific incidents on old versions of Lodestar, please re-open if it happens with latest stable