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.

}
bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
{
    bool fMoreWork = false;
    PeerRef peer = GetPeerRef(pfrom->GetId());
    if (peer == nullptr) return false;
    {
        LOCK(peer->m_getdata_requests_mutex);
        if (!peer->m_getdata_requests.empty()) {
            ProcessGetData(*pfrom, *peer, interruptMsgProc);
        }
    }
    {
        LOCK2(cs_main, g_cs_orphans);
        if (!peer->m_orphan_work_set.empty()) {
            ProcessOrphanTx(peer->m_orphan_work_set);
        }
    }
    if (pfrom->fDisconnect)
        return false;
    
    
    {
        LOCK(peer->m_getdata_requests_mutex);
        if (!peer->m_getdata_requests.empty()) return true;
    }
    {
        LOCK(g_cs_orphans);
        if (!peer->m_orphan_work_set.empty()) return true;
    }