There are some potential feefilter cleanups mentioned and motivated in comment https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-805808485 . If you address the locking one, please be careful and make sure that `round()` is only called under a lock. See https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-807992199

#### Useful skills:

* Bitcoin protocol messages
* Bitcoin Core P2P design
* Running our unit and functional tests

#### Want to work on this issue?

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.

void LoadMempool(const ArgsManager& args);
    
    bool LoadChainTip(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    
    
    
    CoinsCacheSizeState GetCoinsCacheSizeState(const CTxMemPool* tx_pool)
        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
    CoinsCacheSizeState GetCoinsCacheSizeState(
        const CTxMemPool* tx_pool,
        size_t max_coins_cache_size_bytes,
        size_t max_mempool_size_bytes) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
    std::string ToString() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
private:
    bool ActivateBestChainStep(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool.cs);
    bool ConnectTip(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions& disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool.cs);
    void InvalidBlockFound(CBlockIndex *pindex, const BlockValidationState &state) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    CBlockIndex* FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    void ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pindexNew, const FlatFilePos& pos, const Consensus::Params& consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs, const CChainParams& params) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    void CheckForkWarningConditions() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    void InvalidChainFound(CBlockIndex* pindexNew) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    bool LoadBlockIndexDB(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    friend ChainstateManager;
};
/**
 * Provides an interface for creating and interacting with one or two
 * chainstates: an IBD chainstate generated by downloading blocks, and
 * an optional snapshot chainstate loaded from a UTXO snapshot. Managed