Merge pull request #545 from arvidn/zero-cache-perf-1.1

allow each peer have at least 2 allocated disk blocks at any given time

include/libtorrent/disk_buffer_pool.hpp

@@ -135,7 +135,7 @@ namespace libtorrent
 		// of buffers in use drops below the low watermark,
 		// we start calling these functions back
 		// TODO: try to remove the observers, only using the async_allocate handlers
-		std::vector<boost::shared_ptr<disk_observer> > m_observers;
+		std::vector<boost::weak_ptr<disk_observer> > m_observers;
 
 		// these handlers are executed when a new buffer is available
 		std::vector<handler_t> m_handlers;

include/libtorrent/disk_io_job.hpp

@@ -136,11 +136,7 @@ namespace libtorrent
 			in_progress = 0x20,
 
 			// turns into file::coalesce_buffers in the file operation
-			coalesce_buffers = 0x40,
+			coalesce_buffers = 0x40
-
-			// the disk cache was enabled when this job was issued, it should use
-			// the disk cache once it's handled by a disk thread
-			use_disk_cache = 0x80
 		};
 
 		// for write jobs, returns true if its block

include/libtorrent/disk_io_thread.hpp

@@ -1,6 +1,6 @@
 /*
 
-Copyright (c) 2007-2016, Arvid Norberg
+Copyright (c) 2007-2016, Arvid Norberg, Steven Siloti
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

include/libtorrent/settings_pack.hpp

@@ -259,14 +259,16 @@ namespace libtorrent
 			// passes the hash check, it is taken out of parole mode.
 			use_parole_mode,
 
-			// enable and disable caching of read blocks and blocks to be written
+			// enable and disable caching of blocks read from disk. the purpose of
-			// to disk respsectively. the purpose of the read cache is partly
+			// the read cache is partly read-ahead of requests but also to avoid
-			// read-ahead of requests but also to avoid reading blocks back from
+			// reading blocks back from the disk multiple times for popular
-			// the disk multiple times for popular pieces. the write cache purpose
+			// pieces.
-			// is to hold off writing blocks to disk until they have been hashed,
-			// to avoid having to read them back in again.
 			use_read_cache,
+#ifndef TORRENT_NO_DEPRECATED
 			use_write_cache,
+#else
+			deprecated7,
+#endif
 
 			// this will make the disk cache never flush a write piece if it would
 			// cause is to have to re-read it once we want to calculate the piece

src/disk_buffer_pool.cpp

@@ -64,8 +64,10 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent
 {
+	namespace {
+
 	// this is posted to the network thread
-	static void watermark_callback(std::vector<boost::shared_ptr<disk_observer> >* cbs
+	void watermark_callback(std::vector<boost::weak_ptr<disk_observer> >* cbs
 		, std::vector<disk_buffer_pool::handler_t>* handlers)
 	{
 		if (handlers)
@@ -78,13 +80,18 @@ namespace libtorrent
 
 		if (cbs != NULL)
 		{
-			for (std::vector<boost::shared_ptr<disk_observer> >::iterator i = cbs->begin()
+			for (std::vector<boost::weak_ptr<disk_observer> >::iterator i = cbs->begin()
 				, end(cbs->end()); i != end; ++i)
-				(*i)->on_disk();
+			{
+				boost::shared_ptr<disk_observer> o = i->lock();
+				if (o) o->on_disk();
+			}
 			delete cbs;
 		}
 	}
 
+	} // anonymous namespace
+
 	disk_buffer_pool::disk_buffer_pool(int block_size, io_service& ios
 		, boost::function<void()> const& trigger_trim)
 		: m_block_size(block_size)
@@ -183,7 +190,7 @@ namespace libtorrent
 		{
 			l.unlock();
 			m_ios.post(boost::bind(&watermark_callback
-				, static_cast<std::vector<boost::shared_ptr<disk_observer> >*>(NULL)
+				, static_cast<std::vector<boost::weak_ptr<disk_observer> >*>(NULL)
 				, slice));
 			return;
 		}
@@ -195,13 +202,13 @@ namespace libtorrent
 		{
 			l.unlock();
 			m_ios.post(boost::bind(&watermark_callback
-				, static_cast<std::vector<boost::shared_ptr<disk_observer> >*>(NULL)
+				, static_cast<std::vector<boost::weak_ptr<disk_observer> >*>(NULL)
 				, handlers));
 			return;
 		}
 
-		std::vector<boost::shared_ptr<disk_observer> >* cbs
+		std::vector<boost::weak_ptr<disk_observer> >* cbs
-			= new std::vector<boost::shared_ptr<disk_observer> >();
+			= new std::vector<boost::weak_ptr<disk_observer> >();
 		m_observers.swap(*cbs);
 		l.unlock();
 		m_ios.post(boost::bind(&watermark_callback, cbs, handlers));

src/disk_io_thread.cpp

@@ -1,6 +1,6 @@
 /*
 
-Copyright (c) 2007-2016, Arvid Norberg
+Copyright (c) 2007-2016, Arvid Norberg, Steven Siloti
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -1208,14 +1208,6 @@ namespace libtorrent
 
 	int disk_io_thread::do_read(disk_io_job* j, jobqueue_t& completed_jobs)
 	{
-		if ((j->flags & disk_io_job::use_disk_cache) == 0)
-		{
-			// we're not using a cache. This is the simple path
-			// just read straight from the file
-			int ret = do_uncached_read(j);
-			return ret;
-		}
-
 		int block_size = m_disk_cache.block_size();
 		int piece_size = j->storage->files()->piece_size(j->piece);
 		int blocks_in_piece = (piece_size + block_size - 1) / block_size;
@@ -1232,26 +1224,8 @@ namespace libtorrent
 		cached_piece_entry* pe = m_disk_cache.find_piece(j);
 		if (pe == NULL)
 		{
-			// this isn't supposed to happen. The piece is supposed
+			l.unlock();
-			// to be allocated when the read job is posted to the
+			return do_uncached_read(j);
-			// queue, and have 'outstanding_read' set to 1
-			TORRENT_ASSERT(false);
-
-			int cache_state = (j->flags & disk_io_job::volatile_read)
-				? cached_piece_entry::volatile_read_lru
-				: cached_piece_entry::read_lru1;
-			pe = m_disk_cache.allocate_piece(j, cache_state);
-			if (pe == NULL)
-			{
-				j->error.ec = error::no_memory;
-				j->error.operation = storage_error::alloc_cache_piece;
-				m_disk_cache.free_iovec(iov, iov_len);
-				return -1;
-			}
-#if TORRENT_USE_ASSERTS
-			pe->piece_log.push_back(piece_log_t(piece_log_t::set_outstanding_jobs));
-#endif
-			pe->outstanding_read = 1;
 		}
 		TORRENT_PIECE_ASSERT(pe->outstanding_read == 1, pe);
 
@@ -1633,7 +1607,6 @@ namespace libtorrent
 			j->error.operation = storage_error::read;
 			return 0;
 		}
-		j->flags |= disk_io_job::use_disk_cache;
 		if (pe->outstanding_read)
 		{
 			TORRENT_PIECE_ASSERT(j->piece == pe->piece, pe);

src/peer_connection.cpp

@@ -2611,7 +2611,13 @@ namespace libtorrent
 			return;
 		}
 
-		if (exceeded)
+		// every peer is entitled to have two disk blocks allocated at any given
+		// time, regardless of whether the cache size is exceeded or not. If this
+		// was not the case, when the cache size setting is very small, most peers
+		// would be blocked most of the time, because the disk cache would
+		// continously be in exceeded state. Only rarely would it actually drop
+		// down to 0 and unblock all peers.
+		if (exceeded && m_outstanding_writing_bytes > 0)
 		{
 			if ((m_channel_state[download_channel] & peer_info::bw_disk) == 0)
 				m_counters.inc_stats_counter(counters::num_peers_down_disk);
@@ -4541,7 +4547,9 @@ namespace libtorrent
 			return false;
 		}
 
-		if (exceeded)
+		// to understand why m_outstanding_writing_bytes is here, see comment by
+		// the other call to allocate_disk_buffer()
+		if (exceeded && m_outstanding_writing_bytes > 0)
 		{
 #ifndef TORRENT_DISABLE_LOGGING
 			peer_log(peer_log_alert::info, "DISK", "exceeded disk buffer watermark");

src/session_impl.cpp

@@ -1153,17 +1153,6 @@ namespace aux {
 			TORRENT_ASSERT_VAL(conn == int(m_connections.size()) + 1, conn);
 		}
 
-		m_download_rate.close();
-		m_upload_rate.close();
-
-		// #error closing the udp socket here means that
-		// the uTP connections cannot be closed gracefully
-		m_udp_socket.close();
-		m_external_udp_port = 0;
-#ifdef TORRENT_USE_OPENSSL
-		m_ssl_udp_socket.close();
-#endif
-
 		// we need to give all the sockets an opportunity to actually have their handlers
 		// called and cancelled before we continue the shutdown. This is a bit
 		// complicated, if there are no "undead" peers, it's safe tor resume the
@@ -1179,6 +1168,15 @@ namespace aux {
 
 	void session_impl::abort_stage2()
 	{
+		m_download_rate.close();
+		m_upload_rate.close();
+
+		m_udp_socket.close();
+		m_external_udp_port = 0;
+#ifdef TORRENT_USE_OPENSSL
+		m_ssl_udp_socket.close();
+#endif
+
 		// it's OK to detach the threads here. The disk_io_thread
 		// has an internal counter and won't release the network
 		// thread until they're all dead (via m_work).

src/settings_pack.cpp

@@ -150,7 +150,7 @@ namespace libtorrent
 		SET(upnp_ignore_nonrouters, false, 0),
 		SET(use_parole_mode, true, 0),
 		SET(use_read_cache, true, 0),
-		SET(use_write_cache, true, 0),
+		DEPRECATED_SET(use_write_cache, true, 0),
 		SET(dont_flush_write_cache, false, 0),
 		SET(explicit_read_cache, false, 0),
 		SET(coalesce_reads, false, 0),