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

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if (pto->IsInboundConn()) {
                        pto->m_tx_relay->nNextInvSend = m_connman.PoissonNextSendInbound(current_time, INBOUND_INVENTORY_BROADCAST_INTERVAL);
                    } else {
                        pto->m_tx_relay->nNextInvSend = PoissonNextSend(current_time, OUTBOUND_INVENTORY_BROADCAST_INTERVAL);
                    }
                }
                
                if (fSendTrickle) {
                    LOCK(pto->m_tx_relay->cs_filter);
                    if (!pto->m_tx_relay->fRelayTxes) pto->m_tx_relay->setInventoryTxToSend.clear();
                }
                
                if (fSendTrickle && pto->m_tx_relay->fSendMempool) {
                    auto vtxinfo = m_mempool.infoAll();
                    pto->m_tx_relay->fSendMempool = false;
                    const CFeeRate filterrate{pto->m_tx_relay->minFeeFilter.load()};
                    LOCK(pto->m_tx_relay->cs_filter);
                    for (const auto& txinfo : vtxinfo) {
                        const uint256& hash = state.m_wtxid_relay ? txinfo.tx->GetWitnessHash() : txinfo.tx->GetHash();
                        CInv inv(state.m_wtxid_relay ? MSG_WTX : MSG_TX, hash);
                        pto->m_tx_relay->setInventoryTxToSend.erase(hash);
                        
                        if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                            continue;
                        }
                        if (pto->m_tx_relay->pfilter) {
                            if (!pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                        }
                        pto->m_tx_relay->filterInventoryKnown.insert(hash);