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::string GetArg(const std::string& strArg, const std::string& strDefault);
/**
 * Return integer argument or default value
 *
 * @param strArg Argument to get (e.g. "-foo")
 * @param default (e.g. 1)
 * @return command-line argument (0 if invalid number) or default value
 */
int64_t GetArg(const std::string& strArg, int64_t nDefault);
/**
 * Return boolean argument or default value
 *
 * @param strArg Argument to get (e.g. "-foo")
 * @param default (true or false)
 * @return command-line argument or default value
 */
bool GetBoolArg(const std::string& strArg, bool fDefault);
/**
 * Set an argument if it doesn't already have a value
 *
 * @param strArg Argument to set (e.g. "-foo")
 * @param strValue Value (e.g. "1")
 * @return true if argument gets set, false if it already had a value
 */
bool SoftSetArg(const std::string& strArg, const std::string& strValue);
/**
 * Set a boolean argument if it doesn't already have a value
 *
 * @param strArg Argument to set (e.g. "-foo")
 * @param fValue Value (e.g. false)