innodb_log_buffer_size参数最小值

storage/innobase/handler/ha_innodb.cc
static MYSQL_SYSVAR_LONG(log_buffer_size, innobase_log_buffer_size,
  PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
  "The size of the buffer which InnoDB uses to write log to the log files on disk.",
  NULL, NULL, 16*1024*1024L, 256*1024L, LONG_MAX, 1024);

./bin/mysqld --basedir=/data/mysql_debug --datadir=/data/mysql_debug/data --innodb-log-buffer-size=131072

mysql> show variables like '%log_buffer%';
+------------------------+--------+
| Variable_name          | Value  |
+------------------------+--------+
| innodb_log_buffer_size | 262144 |
+------------------------+--------+

(gdb) p *log_sys
$2 = {
...
  buf_size = 262144,
  max_buf_free = 63488,
...
}