Memory usage of non-validator nodes grows indefinitely, leading to OOM and unclean shutdown about quorum

[hhsel]

Executing debug.writeMemProfile() every 15 minutes for 2 months showed that, among go tool pprof entries, the following entries are growing constantly, finally causing OOM:

• github.com/ethereum/go-ethereum/consensus/istanbul/validator.newDefaultSet
• github.com/ethereum/go-ethereum/consensus/istanbul/validator.New (inline)

validator.newDefaultSet calls policy.RegisterValidatorSet() and add a validator set to validator set list called registry inside ProposerPolicy. It seems that this function is called at least once in the block production process.
It seems that the only way to clear this array is calling ClearRegistry(), but this is only called in Commit(), so non-validator nodes does not call this function, accumulating validator sets indefinitely.

I don't know why validator nodes also accumulating these validator sets in the same manner and sudden memory usage drops occur, because validator nodes call Commit() every block so registry is expected to keep relarively small.