make disk cache pool allocator configurable

ChangeLog

@@ -1,3 +1,4 @@
+	* make disk cache pool allocator configurable
 	* fix library ABI to not depend on logging being enabled
 	* use hex encoding instead of base32 in create_magnet_uri
 	* include name, save_path and torrent_file in torrent_status, for improved performance

docs/manual.rst

@@ -4654,6 +4654,12 @@ session_settings
 
 		bool ban_web_seeds;
 		int max_http_recv_buffer_size;
+
+		bool support_share_mode;
+		bool support_merkle_torrents;
+		bool report_redundant_bytes;
+		std::string handshake_client_version;
+		bool use_disk_cache_pool;
 	};
 
 ``version`` is automatically set to the libtorrent version you're using
@@ -5556,6 +5562,23 @@ RAM buffers when downloading stuff over HTTP. Specifically when specifying a
 URL to a .torrent file when adding a torrent or when announcing to an HTTP
 tracker. The default is 2 MiB.
 
+``support_share_mode`` enables or disables the share mode extension. This is
+enabled by default.
+
+``support_merkle_torrents`` enables or disables the merkle tree torrent support.
+This is enabled by default.
+
+``report_redundant_bytes`` enables or disables reporting redundant bytes to the tracker.
+This is enabled by default.
+
+``handshake_client_version`` is the client name advertized in the peer handshake. If
+set to an empty string, the user_agent string is used.
+
+``use_disk_cache_pool`` enables using a pool allocator for disk cache blocks. This is
+disabled by default. Enabling it makes the cache perform better at high throughput.
+It also makes the cache less likely and slower at returning memory back to the system
+once allocated.
+
 pe_settings
 ===========
 

include/libtorrent/disk_buffer_pool.hpp

@@ -38,6 +38,10 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/session_settings.hpp"
 #include "libtorrent/allocator.hpp"
 
+#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
+#include <boost/pool/pool.hpp>
+#endif
+
 #ifdef TORRENT_DISK_STATS
 #include <fstream>
 #endif
@@ -97,6 +101,25 @@ namespace libtorrent
 
 		mutable mutex m_pool_mutex;
 
+#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
+		// if this is true, all buffers are allocated
+		// from m_pool. If this is false, all buffers
+		// are allocated using page_aligned_allocator.
+		// if the settings change to prefer the other
+		// allocator, this bool will not switch over
+		// to match the settings until all buffers have
+		// been freed. That way, we never have a mixture
+		// of buffers allocated from different sources.
+		// in essence, this make the setting only take
+		// effect after a restart (which seems fine).
+		// or once the client goes idle for a while.
+		bool m_using_pool_allocator;
+
+		// memory pool for read and write operations
+		// and disk cache
+		boost::pool<page_aligned_allocator> m_pool;
+#endif
+
 #if defined TORRENT_DISK_STATS || defined TORRENT_STATS
 		int m_allocations;
 #endif

include/libtorrent/session_settings.hpp

@@ -965,6 +965,14 @@ namespace libtorrent
 		// in the peer protocol handshake. If this is empty
 		// the user_agent is used
 		std::string handshake_client_version;
+
+		// if this is true, the disk cache uses a pool allocator
+		// for disk cache blocks. Enabling this improves
+		// performance of the disk cache with the side effect
+		// that the disk cache is less likely and slower at
+		// returning memory to the kernel when cache pressure
+		// is low.
+		bool use_disk_cache_pool;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

include/libtorrent/torrent_handle.hpp

@@ -127,7 +127,7 @@ namespace libtorrent
 	private:
 		// the type of the addr union
 		unsigned is_v6_addr:1;
-		unsigned unused:1;
+//		unsigned unused:1;
 	public:
 		// the state this block is in (see block_state_t)
 		unsigned state:2;

src/disk_buffer_pool.cpp

@@ -47,6 +47,10 @@ namespace libtorrent
 	disk_buffer_pool::disk_buffer_pool(int block_size)
 		: m_block_size(block_size)
 		, m_in_use(0)
+#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
+		, m_using_pool_allocator(false)
+		, m_pool(block_size, m_settings.cache_buffer_chunk_size)
+#endif
 	{
 #if defined TORRENT_DISK_STATS || defined TORRENT_STATS
 		m_allocations = 0;
@@ -80,7 +84,14 @@ namespace libtorrent
 		if (m_buf_to_category.find(buffer)
 			== m_buf_to_category.end()) return false;
 #endif
+#ifdef TORRENT_DISABLE_POOL_ALLOCATOR
 		return true;
+#else
+		if (m_using_pool_allocator)
+			return m_pool.is_from(buffer);
+		else
+			return true;
+#endif
 	}
 
 	bool disk_buffer_pool::is_disk_buffer(char* buffer) const
@@ -94,7 +105,20 @@ namespace libtorrent
 	{
 		mutex::scoped_lock l(m_pool_mutex);
 		TORRENT_ASSERT(m_magic == 0x1337);
-		char* ret = page_aligned_allocator::malloc(m_block_size);
+		char* ret;
+#ifdef TORRENT_DISABLE_POOL_ALLOCATOR
+		ret = page_aligned_allocator::malloc(m_block_size);
+#else
+		if (m_using_pool_allocator)
+		{
+			ret = (char*)m_pool.malloc();
+			m_pool.set_next_size(m_settings.cache_buffer_chunk_size);
+		}
+		else
+		{
+			ret = page_aligned_allocator::malloc(m_block_size);
+		}
+#endif
 		++m_in_use;
 #if TORRENT_USE_MLOCK
 		if (m_settings.lock_disk_cache)
@@ -185,13 +209,34 @@ namespace libtorrent
 #endif		
 		}
 #endif
+#ifdef TORRENT_DISABLE_POOL_ALLOCATOR
 		page_aligned_allocator::free(buf);
+#else
+		if (m_using_pool_allocator)
+			m_pool.free(buf);
+		else
+			page_aligned_allocator::free(buf);
+#endif
 		--m_in_use;
+
+#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
+		// should we switch which allocator to use?
+		if (m_in_use == 0 && m_settings.use_disk_cache_pool != m_using_pool_allocator)
+		{
+			m_pool.release_memory();
+			m_using_pool_allocator = m_settings.use_disk_cache_pool;
+		}
+#endif
 	}
 
 	void disk_buffer_pool::release_memory()
 	{
 		TORRENT_ASSERT(m_magic == 0x1337);
+#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
+		mutex::scoped_lock l(m_pool_mutex);
+		if (m_using_pool_allocator)
+			m_pool.release_memory();
+#endif
 	}
 }
 

src/session.cpp

@@ -304,6 +304,9 @@ namespace libtorrent
 		// max 'bottled' http receive buffer/url torrent size
 		set.max_http_recv_buffer_size = 6 * 1024 * 1024;
 
+		// the disk cache performs better with the pool allocator
+		set.use_disk_cache_pool = true;
+
 		return set;
 	}
 
@@ -1312,6 +1315,7 @@ namespace libtorrent
 		, support_share_mode(true)
 		, support_merkle_torrents(false)
 		, report_redundant_bytes(true)
+		, use_disk_cache_pool(false)
 	{}
 
 	session_settings::~session_settings() {}