MDEV-14114 Intoduce variable for binlog io cache size.

mysql-test/r/mysqld--help.result

@@ -67,6 +67,8 @@ The following options may be given as the first argument:
  --binlog-do-db=name Tells the master it should log updates for the specified
  database, and exclude all others not explicitly
  mentioned.
+ --binlog-file-cache-size=# 
+ The size of file cache for the binary log
  --binlog-format=name 
  What form of binary logging the master will use: either
  ROW for row-based binary logging, STATEMENT for
@@ -1290,6 +1292,7 @@ binlog-checksum CRC32
 binlog-commit-wait-count 0
 binlog-commit-wait-usec 100000
 binlog-direct-non-transactional-updates FALSE
+binlog-file-cache-size 16384
 binlog-format MIXED
 binlog-optimize-thread-scheduling TRUE
 binlog-row-event-max-size 8192

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -220,6 +220,20 @@ NUMERIC_BLOCK_SIZE	NULL
 ENUM_VALUE_LIST	OFF,ON
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	OPTIONAL
+VARIABLE_NAME	BINLOG_FILE_CACHE_SIZE
+SESSION_VALUE	NULL
+GLOBAL_VALUE	16384
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	16384
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	BIGINT UNSIGNED
+VARIABLE_COMMENT	The size of file cache for the binary log
+NUMERIC_MIN_VALUE	8192
+NUMERIC_MAX_VALUE	18446744073709551615
+NUMERIC_BLOCK_SIZE	4096
+ENUM_VALUE_LIST	NULL
+READ_ONLY	NO
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	BINLOG_FORMAT
 SESSION_VALUE	MIXED
 GLOBAL_VALUE	MIXED

sql/log.cc

@@ -2391,7 +2391,7 @@ File open_binlog(IO_CACHE *log, const char *log_file_name, const char **errmsg)
     *errmsg = "Could not open log file";
     goto err;
   }
-  if (init_io_cache(log, file, IO_SIZE*2, READ_CACHE, 0, 0,
+  if (init_io_cache(log, file, binlog_file_cache_size, READ_CACHE, 0, 0,
                     MYF(MY_WME|MY_DONT_CHECK_FILESIZE)))
   {
     sql_print_error("Failed to create a cache on log (file '%s')",

sql/mysqld.cc

@@ -506,6 +506,7 @@ ulong slave_ddl_exec_mode_options= SLAVE_EXEC_MODE_IDEMPOTENT;
 ulonglong slave_type_conversions_options;
 ulong thread_cache_size=0;
 ulonglong binlog_cache_size=0;
+ulonglong binlog_file_cache_size=0;
 ulonglong max_binlog_cache_size=0;
 ulong slave_max_allowed_packet= 0;
 ulonglong binlog_stmt_cache_size=0;

sql/mysqld.h

@@ -214,7 +214,7 @@ extern volatile ulong cached_thread_count;
 extern ulong what_to_log,flush_time;
 extern ulong max_prepared_stmt_count, prepared_stmt_count;
 extern ulong open_files_limit;
-extern ulonglong binlog_cache_size, binlog_stmt_cache_size;
+extern ulonglong binlog_cache_size, binlog_stmt_cache_size, binlog_file_cache_size;
 extern ulonglong max_binlog_cache_size, max_binlog_stmt_cache_size;
 extern ulong max_binlog_size;
 extern ulong slave_max_allowed_packet;

sql/sys_vars.cc

@@ -396,6 +396,13 @@ static Sys_var_ulonglong Sys_binlog_cache_size(
        CMD_LINE(REQUIRED_ARG),
        VALID_RANGE(IO_SIZE, SIZE_T_MAX), DEFAULT(32768), BLOCK_SIZE(IO_SIZE));
 
+static Sys_var_ulonglong  Sys_binlog_file_cache_size(
+       "binlog_file_cache_size", 
+       "The size of file cache for the binary log", 
+       GLOBAL_VAR(binlog_file_cache_size),
+       CMD_LINE(REQUIRED_ARG),
+       VALID_RANGE(IO_SIZE*2, SIZE_T_MAX), DEFAULT(IO_SIZE*4), BLOCK_SIZE(IO_SIZE));
+
 static Sys_var_ulonglong Sys_binlog_stmt_cache_size(
        "binlog_stmt_cache_size", "The size of the statement cache for "
        "updates to non-transactional engines for the binary log. "