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?

{
    fflush(fileout); 
#ifdef WIN32
    HANDLE hFile = (HANDLE)_get_osfhandle(_fileno(fileout));
    FlushFileBuffers(hFile);
#else
    #if defined(__linux__) || defined(__NetBSD__)
    fdatasync(fileno(fileout));
    #elif defined(__APPLE__) && defined(F_FULLFSYNC)
    fcntl(fileno(fileout), F_FULLFSYNC, 0);
    #else
    fsync(fileno(fileout));
    #endif
#endif
}
bool TruncateFile(FILE *file, unsigned int length) {
#if defined(WIN32)
    return _chsize(_fileno(file), length) == 0;
#else
    return ftruncate(fileno(file), length) == 0;
#endif
}
/**
 * this function tries to raise the file descriptor limit to the requested number.
 * It returns the actual file descriptor limit (which may be more or less than nMinFD)
 */
int RaiseFileDescriptorLimit(int nMinFD) {