--- 公众号 MySQL学习 随便记录点 5.7.22代码 MySQL工具主要分为 交互式和非交互式 - 交互式 就是我们平时用的交互式命令方式 - 非交互式（batch mode） 主要用于解析binlog和批量导入sql，每次都会读取1行数据到buffer 如果是binlog，那么每次大约读取的原始数据为76字节，及mysqlbinlog解析出来的一行 ``` AAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAA AAAAAP4AAAAAAAAAAP4KAAAAAAAAAP4UAAAAAAAAAP4eAAAAAAAAAP4oAAAAAAAAAP4yAAAAAAAA AP48AAAAAAAAAP5GAAAAAAAAAP5QAAAAAAAAAP5aAAAAAAAAAP4KAAAAAAAAAP4AAAAAAAAAAP4A AAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4AAAAA AAAAAP4AAAAAAAAAAP4AAAAAAAAAAP4KAAAAAAAAAP4UAAAAAAAAAP4eAAAAAAAAAP4oAAAAAAAA AP4yAAAAAAAAAP48AAAAAAAAAP5GAAAAAAAAAP5QAAAAAAAAAP5aAAAAAAAAAP4KAAAAAAAAAP4A ``` 类似这里就有6行。如果是大事务，每次解析76字节，add_line 函数。然后等待大事务所有行解析完成后进行com_do函数进行执行命令。 如果是sql语句，那么就是一条sql执行一次没有什么问题。 最近遇到mysqlbinlog|mysql大事务特别慢的情况，因此提交了如下问题： https://bugs.mysql.com/bug.php?id=102278 8.0.13修复了，5.7.33最新版本依旧存在这个问题。 ``` Hi: we use mysqlbinlog|mysql to parse binlog and recover binlog,when have large trasaction,mysql client tool is very slow at add_line function. 20M trasaction event mysql add line use 1 hour!! cpu is 100% use in sy% and pstack mysql client stack like: __memmove_sse3 my_realloc String::mem_realloc add_line read_and_execute main when batch mode,mysql every time add 76 bytes event line to buffer,buffer init 520 bytes,when 20M event load in buffer then call com_do funcation to execute command。 Breakpoint 9, add_line (buffer=..., line=0xa603e0 "/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;", line_length=45, in_string=0x7fffffffe287 "", ml_comment=0x7fffffffe286, truncated=false) at /opt/percona-server-locks-detail-5.7.22/client/mysql.cc:2533 2533 bool need_space= 0; (gdb) p buffer.m_length $20 = 0 (gdb) p buffer.m_alloced_length $21 = 520 when buffer is smaller, every time allocate 4K mem: if (buffer.length() + length >= buffer.alloced_length()) buffer.mem_realloc(buffer.length()+length+IO_SIZE); this step rise frequently mem allocate.and cpu sy% is very high!! when mysql use batch mode can we use large init buffer or give our a parameter to control this. when i search bug i find Bug #85155 is like this,is this fix at mysql 8.0.13,what 5.7 version fix this? thanks!! ``` 我进行了一下修改，如下： ``` mysql.cc main函数下 MAX_BATCH_BUFFER_SIZE 已经定义好为1G glob_buffer.mem_realloc(MAX_BATCH_BUFFER_SIZE); [root@mgr3 client]# /opt/my_mysql/bin/mysqlbinlog /opt/bin/log_bin.000002 |/opt/my_mysql/bin/mysql 速度极快了 [root@mgr3 client]# /opt/my_mysql/bin/mysqlbinlog /opt/bin/log_bin.000002 |/opt/my_mysql/bin/mysqlbak CPU 99% 位于192.168.1.63 上的/opt/my_mysql/bin/mysqlbak目录下，如果再次遇到这种问题，可以使用修改过的进行执行。 ```