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?

{
#ifdef WIN32
    return MoveFileExA(src.string().c_str(), dest.string().c_str(),
                       MOVEFILE_REPLACE_EXISTING) != 0;
#else
    int rc = std::rename(src.string().c_str(), dest.string().c_str());
    return (rc == 0);
#endif 
}
/**
 * Ignores exceptions thrown by Boost's create_directory if the requested directory exists.
 * Specifically handles case where path p exists, but it wasn't possible for the user to
 * write to the parent directory.
 */
bool TryCreateDirectory(const boost::filesystem::path& p)
{
    try
    {
        return boost::filesystem::create_directory(p);
    } catch (const boost::filesystem::filesystem_error&) {
        if (!boost::filesystem::exists(p) || !boost::filesystem::is_directory(p))
            throw;
    }
    
    return false;
}
void FileCommit(FILE *fileout)