Continuing this series, Part 4 touches on two disparate EIPs. Below we will explain the consensus layer specific EIP-7514, which will alter the validator churn limit, and EIP-1153, which will introduce transient storage op-codes in the EVM (execution layer).
Part 1 of this series explored the opcode-focused EIPs 5656 and 6780.
Part 2 of this series focused on two staking and validator upgrades: EIP-7044 and EIP-7045.
Part 3 detailed the implications of EIP-4788, and how communication between the consensus and execution layers has evolved.
Ethereum EIP-7514: Add Max Epoch Churn Limit
EIP-7514 will establish a cap on the per-epoch churn limit at 8, thereby transitioning the maximum growth rate of Ethereum validators from exponential to linear. Ethereum’s churn limit defines the maximum number of validators that can enter (or exit) the active set of Ethereum validators every epoch (~6.4 minutes). The churn limit is currently a variable that has a minimum value of four and increases by one each time a specific number of validators (65,536 or the churn limit quotient) joins the active set.
This proposal – to cap Ethereum’s churn limit at 8 – aims to slow down the growth of the validator set and is desirable because having too many active validators can lead to state-size bloat, which places additional strain on each node as they strive to keep track of their peers. Implementing EIP-7514 should allow time for research into more comprehensive solutions and for community consensus around them to emerge. Testnet simulations prompted this EIPs inclusion, in which client software struggled to adequately perform past 2 million validators.
At the time this EIP was decided for mainnet inclusion, there were ~800K active validators. It was, however, the rate of this increase, and not the total number of validators, that was concerning and the impetus for this EIP’s inclusion. The situation appears less dire with the benefit of retrospect; at the time of writing, the validator entry queue has shortened considerably. Still, validator growth is correlated with the overall market, which is wont to change on a whim.
Entry, not Exit
Importantly, this churn limit change will be limited to entry into Ethereum’s active validator set, and will not be applied to exiting validators. This follows the rationale for EIP-7514, as the primary concern is validator bloat.