wakes up the disk io thread once a second to flush caches

src/disk_io_thread.cpp

@@ -1016,7 +1016,13 @@ namespace libtorrent
 			mutex_t::scoped_lock jl(m_queue_mutex);
 
 			while (m_jobs.empty() && !m_abort)
-				m_signal.wait(jl);
+			{
+				// if there hasn't been an event in one second
+				// see if we should flush the cache
+				if (!m_signal.timed_wait(jl, boost::get_system_time() + boost::posix_time::seconds(1)))
+					flush_expired_pieces();
+			}
+
 			if (m_abort && m_jobs.empty())
 			{
 				jl.unlock();