deprecate settings_pack::hashing_threads and replace it with aio_threads in documentation

docs/hacking.rst

@@ -119,7 +119,7 @@ libtorrent starts 3 to 5 threads.
  * The third thread is the SHA-1 hash thread. By default there's only one hash thread,
    but on multi-core machines downloading at very high rates, libtorrent can be configured
    to start any number of hashing threads, to take full use of multi core systems.
-   (see ``settings_pack::hashing_threads``).
+   (see ``settings_pack::aio_threads``).
 
  * The fourth and fifth threads are spawned by asio on systems that don't support
    asynchronous host name resolution, in order to simulate non-blocking ``getaddrinfo()``.

docs/tuning.rst

@@ -332,12 +332,12 @@ and ``settings_pack::active_seeds``.
 SHA-1 hashing
 -------------
 
-When downloading at very high rates, it is possible to have the CPU be the bottleneck
-for passing every downloaded byte through SHA-1. In order to enable calculating SHA-1
-hashes in parallel, on multi-core systems, set ``settings_pack::hashing_threads``
-to the number of threads libtorrent should start to do SHA-1 hashing. This defaults
-to 1, and only if that thread is close to saturating one core does it make sense to
-increase the number of threads.
+When downloading at very high rates, it is possible to have the CPU be the
+bottleneck for passing every downloaded byte through SHA-1. In order to enable
+calculating SHA-1 hashes in parallel, on multi-core systems, set
+``settings_pack::aio_threads`` to the number of threads libtorrent should
+perform I/O and do SHA-1 hashing in. Only if that thread is close to saturating
+one core does it make sense to increase the number of threads.
 
 scalability
 ===========

examples/client_test.cpp

@@ -1243,7 +1243,7 @@ int main(int argc, char* argv[])
 			"                        previous command line options, so be sure to specify this first\n"
 			"  -G                    Add torrents in seed-mode (i.e. assume all pieces\n"
 			"                        are present and check hashes on-demand)\n"
-			"  -E <num-threads>      specify how many hashing threads to use\n"
+			"  -E <num-threads>      specify how many disk I/O threads to use\n"
 			"\n BITTORRENT OPTIONS\n"
 			"  -c <limit>            sets the max number of connections\n"
 			"  -T <limit>            sets the max number of connections per torrent\n"
@@ -1401,7 +1401,7 @@ int main(int argc, char* argv[])
 			case 'B': settings.set_int(settings_pack::peer_timeout, atoi(arg)); break;
 			case 'n': settings.set_bool(settings_pack::announce_to_all_tiers, true); --i; break;
 			case 'G': seed_mode = true; --i; break;
-			case 'E': settings.set_int(settings_pack::hashing_threads, atoi(arg)); break;
+			case 'E': settings.set_int(settings_pack::aio_threads, atoi(arg)); break;
 			case 'd': settings.set_int(settings_pack::download_rate_limit, atoi(arg) * 1000); break;
 			case 'u': settings.set_int(settings_pack::upload_rate_limit, atoi(arg) * 1000); break;
 			case 'S':

include/libtorrent/settings_pack.hpp

@@ -1387,6 +1387,9 @@ namespace libtorrent
 			// received by the metadata extension, i.e. magnet links.
 			max_metadata_size,
 
+#ifndef TORRENT_NO_DEPRECATE
+			// DEPRECTED: use aio_threads instead
+
 			// ``hashing_threads`` is the number of threads to use for piece hash
 			// verification. It defaults to 1. For very high download rates, on
 			// machines with multiple cores, this could be incremented. Setting it
@@ -1394,6 +1397,9 @@ namespace libtorrent
 			// any benefit of setting it to the number of cores. If it's set to 0,
 			// hashing is done in the disk thread.
 			hashing_threads,
+#else
+			deprecated9,
+#endif
 
 			// the number of blocks to keep outstanding at any given time when
 			// checking torrents. Higher numbers give faster re-checks but uses

src/create_torrent.cpp

@@ -282,7 +282,7 @@ namespace libtorrent
 
 		settings_pack sett;
 		sett.set_int(settings_pack::cache_size, 0);
-		sett.set_int(settings_pack::hashing_threads, 2);
+		sett.set_int(settings_pack::aio_threads, 2);
 
 		// TODO: this should probably be optional
 		alert_manager dummy2(0, 0);

src/session.cpp

@@ -97,7 +97,6 @@ namespace libtorrent
 		set.set_int(settings_pack::checking_mem_usage, 2);
 
 		// don't use any extra threads to do SHA-1 hashing
-		set.set_int(settings_pack::hashing_threads, 0);
 		set.set_int(settings_pack::network_threads, 0);
 		set.set_int(settings_pack::aio_threads, 1);
 
@@ -274,11 +273,6 @@ namespace libtorrent
 		// connect to us if they want to
 		set.set_int(settings_pack::max_failcount, 1);
 
-		// we're likely to have more than 4 cores on a high
-		// performance machine. One core is needed for the
-		// network thread
-		set.set_int(settings_pack::hashing_threads, 4);
-
 		// the number of threads to use to call async_write_some
 		// and read_some on peer sockets
 		// this doesn't work. See comment in settings_pack.cpp

src/settings_pack.cpp

@@ -316,7 +316,7 @@ namespace libtorrent
 		SET(torrent_connect_boost, 10, 0),
 		SET(alert_queue_size, 1000, &session_impl::update_alert_queue_size),
 		SET(max_metadata_size, 3 * 1024 * 10240, 0),
-		SET(hashing_threads, 1, 0),
+		DEPRECATED_SET(hashing_threads, 1, 0),
 		SET(checking_mem_usage, 256, 0),
 		SET(predictive_piece_announce, 0, 0),
 		SET(aio_threads, 4, &session_impl::update_disk_threads),