merged RC_1_1 into master

ChangeLog

@@ -85,6 +85,7 @@
 	* resume data no longer has timestamps of files
 	* require C++11 to build libtorrent
 
+	* coalesce reads and writes by default on windows
 	* fixed disk I/O performance of checking hashes and creating torrents
 	* fix race condition in part_file
 	* fix part_file open mode compatibility test

src/create_torrent.cpp

@@ -296,11 +296,11 @@ namespace {
 
 		settings_pack sett;
 		sett.set_int(settings_pack::cache_size, 0);
-		sett.set_int(settings_pack::aio_threads, 1);
+		sett.set_int(settings_pack::aio_threads, 3);
 
 		disk_thread.set_settings(&sett);
 
-		int const piece_read_ahead = std::max(1, 15 * 1024 * 1024 / t.piece_length());
+		int const piece_read_ahead = std::max(6, 16 * 1024 * 1024 / t.piece_length());
 
 		hash_state st = { t, std::move(storage), disk_thread, piece_index_t(0), piece_index_t(0), f, ec };
 		for (piece_index_t i(0); i < piece_index_t(piece_read_ahead); ++i)

src/settings_pack.cpp

@@ -141,8 +141,17 @@ constexpr int CLOSE_FILE_INTERVAL = 0;
 		SET(use_read_cache, true, nullptr),
 		DEPRECATED_SET(use_write_cache, true, nullptr),
 		DEPRECATED_SET(dont_flush_write_cache, false, nullptr),
+#ifdef TORRENT_WINDOWS
+		// the emulation of preadv/pwritev uses overlapped reads/writes to be able
+		// to issue them all back to back. However, it appears windows fail to
+		// merge them. At least for people reporting performance issues in
+		// qBittorrent
+		SET(coalesce_reads, true, nullptr),
+		SET(coalesce_writes, true, nullptr),
+#else
 		SET(coalesce_reads, false, nullptr),
 		SET(coalesce_writes, false, nullptr),
+#endif
 		SET(auto_manage_prefer_seeds, false, nullptr),
 		SET(dont_count_slow_torrents, true, &session_impl::update_count_slow),
 		SET(close_redundant_connections, true, nullptr),
@@ -306,7 +315,7 @@ constexpr int CLOSE_FILE_INTERVAL = 0;
 		SET(alert_queue_size, 1000, &session_impl::update_alert_queue_size),
 		SET(max_metadata_size, 3 * 1024 * 10240, nullptr),
 		DEPRECATED_SET(hashing_threads, 1, nullptr),
-		SET(checking_mem_usage, 256, nullptr),
+		SET(checking_mem_usage, 1024, nullptr),
 		SET(predictive_piece_announce, 0, nullptr),
 		SET(aio_threads, 4, &session_impl::update_disk_threads),
 		SET(aio_max, 300, nullptr),

test/test_transfer.cpp

@@ -494,6 +494,26 @@ TORRENT_TEST(coalesce_writes)
 	cleanup();
 }
 
+TORRENT_TEST(no_coalesce_reads)
+{
+	using namespace libtorrent;
+	settings_pack p;
+	p.set_int(settings_pack::read_cache_line_size, 16);
+	p.set_bool(settings_pack::coalesce_reads, false);
+	test_transfer(0, p);
+
+	cleanup();
+}
+
+TORRENT_TEST(no_coalesce_writes)
+{
+	using namespace libtorrent;
+	settings_pack p;
+	p.set_bool(settings_pack::coalesce_writes, false);
+	test_transfer(0, p);
+
+	cleanup();
+}
 
 TORRENT_TEST(allocate)
 {