added performance warnings for when the IP overhead eats up the entire up- or download rate limit

docs/manual.rst

@@ -4368,6 +4368,8 @@ upload or download rate performance.
 		{
 			outstanding_disk_buffer_limit_reached,
 			outstanding_request_limit_reached,
+			upload_limit_too_low,
+			download_limit_too_low
 		};
 
 		performance_warning_t warning_code;

include/libtorrent/alert_types.hpp

@@ -158,7 +158,9 @@ namespace libtorrent
 		enum performance_warning_t
 		{
 			outstanding_disk_buffer_limit_reached,
-			outstanding_request_limit_reached
+			outstanding_request_limit_reached,
+			upload_limit_too_low,
+			download_limit_too_low
 		};
 
 		performance_alert(torrent_handle const& h
@@ -177,6 +179,8 @@ namespace libtorrent
 			{
 				"max outstanding disk writes reached",
 				"max outstanding piece requests reached",
+				"upload limit too low (download rate will suffer)",
+				"download limit too low (upload rate will suffer)"
 			};
 
 			return torrent_alert::message() + ": performance warning: "

src/session_impl.cpp

@@ -1104,11 +1104,25 @@ namespace aux {
 			+ m_stat.download_dht()
 			+ m_stat.download_tracker());
 
+		if (m_stat.download_ip_overhead() >= m_download_channel.throttle()
+			&& m_alerts.should_post<performance_alert>())
+		{
+			m_alerts.post_alert(performance_alert(torrent_handle()
+				, performance_alert::download_limit_too_low));
+		}
+
 		m_upload_channel.drain(
 			m_stat.upload_ip_overhead()
 			+ m_stat.upload_dht()
 			+ m_stat.upload_tracker());
 
+		if (m_stat.upload_ip_overhead() >= m_upload_channel.throttle()
+			&& m_alerts.should_post<performance_alert>())
+		{
+			m_alerts.post_alert(performance_alert(torrent_handle()
+				, performance_alert::upload_limit_too_low));
+		}
+
 		m_stat.second_tick(tick_interval);
 
 		// --------------------------------------------------------------