During some lock debugging on a dual-core Linux system I noticed that threads are blocked acquiring `cs_vNodes` and `cs_main` for long periods when the system is under moderate load from unrelated processes -- the unlucky lock acquirer is waiting for single-digit seconds once every 10 minutes or so (not coinciding with new blocks) up to around a 30 second wait every few hours. It looks like `ThreadMessageHandler` is taking locks and then due to being set to `THREAD_PRIORITY_BELOW_NORMAL`, it's being descheduled (even in trivial lock-holding regions like `GetHeight`) and holding up for arbitrarily long periods other threads that use these core locks.

So I'm wondering, what are the benefits of running the message handler at low priority?

std::deque<CSerializeData>::iterator it = vSendMsg.insert(vSendMsg.end(), CSerializeData());
    ssSend.GetAndClear(*it);
    nSendSize += (*it).size();
    
    if (it == vSendMsg.begin())
        SocketSendData(this);
    LEAVE_CRITICAL_SECTION(cs_vSend);
}
CBanDB::CBanDB()
{
    pathBanlist = GetDataDir() / "banlist.dat";
}
bool CBanDB::Write(const banmap_t& banSet)
{
    
    unsigned short randv = 0;
    GetRandBytes((unsigned char*)&randv, sizeof(randv));
    std::string tmpfn = strprintf("banlist.dat.%04x", randv);
    
    CDataStream ssBanlist(SER_DISK, CLIENT_VERSION);
    ssBanlist << FLATDATA(Params().MessageStart());
    ssBanlist << banSet;
    uint256 hash = Hash(ssBanlist.begin(), ssBanlist.end());
    ssBanlist << hash;
    
    boost::filesystem::path pathTmp = GetDataDir() / tmpfn;
    FILE *file = fopen(pathTmp.string().c_str(), "wb");
    CAutoFile fileout(file, SER_DISK, CLIENT_VERSION);
    if (fileout.IsNull())
        return error("%s: Failed to open file %s", __func__, pathTmp.string());