tweak the auto-cache-size logic to have slightly smaller cache

examples/client_test.cpp

@@ -484,7 +484,7 @@ int poll_interval = 5;
 int max_connections_per_torrent = 50;
 bool seed_mode = false;
 bool stats_enabled = false;
-int cache_size = 1024;
+int cache_size = -1;
 
 bool share_mode = false;
 bool disable_storage = false;

include/libtorrent/settings_pack.hpp

@@ -979,9 +979,9 @@ namespace libtorrent {
 			// or receive buffer also count against this limit. Send and receive
 			// buffers will never be denied to be allocated, but they will cause
 			// the actual cached blocks to be flushed or evicted. If this is set
-			// to -1, the cache size is automatically set to the amount of
-			// physical RAM available in the machine divided by 8. If the amount
-			// of physical RAM cannot be determined, it's set to 1024 (= 16 MiB).
+			// to -1, the cache size is automatically set based on the amount of
+			// physical RAM on the machine. If the amount of physical RAM cannot
+			// be determined, it's set to 1024 (= 16 MiB).
 			//
 			// ``cache_expiry`` is the number of seconds from the last cached write
 			// to a piece in the write cache, to when it's forcefully flushed to
@@ -1593,7 +1593,7 @@ namespace libtorrent {
 			out_enc_policy,
 			in_enc_policy,
 
-			// determines the encryption level of the connections.  This setting
+			// determines the encryption level of the connections. This setting
 			// will adjust which encryption scheme is offered to the other peer,
 			// as well as which encryption scheme is selected by the client. See
 			// enc_level enum for options.

src/disk_buffer_pool.cpp

@@ -303,8 +303,8 @@ namespace libtorrent {
 				// The more physical RAM, the smaller portion of it is allocated
 				// for the cache.
 
-				// we take a 30th of everything exceeding 4 GiB
-				// a 20th of everything exceeding 1 GiB
+				// we take a 40th of everything exceeding 4 GiB
+				// a 30th of everything exceeding 1 GiB
 				// and a 10th of everything below a GiB
 
 				constexpr std::int64_t gb = 1024 * 1024 * 1024;
@@ -312,15 +312,15 @@ namespace libtorrent {
 				std::int64_t result = 0;
 				if (phys_ram > 4 * gb)
 				{
-					result += (phys_ram - 4 * gb) / 30;
+					result += (phys_ram - 4 * gb) / 40;
 					phys_ram = 4 * gb;
 				}
 				if (phys_ram > 1 * gb)
 				{
-					result += (phys_ram - 1 * gb) / 20;
+					result += (phys_ram - 1 * gb) / 30;
 					phys_ram = 1 * gb;
 				}
-				result += phys_ram / 10;
+				result += phys_ram / 20;
 				m_max_use = int(result / default_block_size);
 			}
 

src/settings_pack.cpp

@@ -248,7 +248,7 @@ constexpr int CLOSE_FILE_INTERVAL = 0;
 		SET(send_buffer_watermark_factor, 50, nullptr),
 		SET(choking_algorithm, settings_pack::fixed_slots_choker, nullptr),
 		SET(seed_choking_algorithm, settings_pack::round_robin, nullptr),
-		SET(cache_size, 1024, nullptr),
+		SET(cache_size, 2048, nullptr),
 		DEPRECATED_SET(cache_buffer_chunk_size, 0, nullptr),
 		SET(cache_expiry, 300, nullptr),
 		SET(disk_io_write_mode, settings_pack::enable_os_cache, nullptr),