**在InnoDB存储引擎中大量使用AIO来处理IO请求,而I/O Thread主要负责处理这些 I/O 请求的回调(call back)处理。**这里共有四类I/O线程,分别是:insert buffer thread、log thread、read thread、write thread。 mysql> show variables like "%innodb%io_threads%"; +---+---+ | Variable_name | Value |...
write_notifier, &log); | |--> os_thread_create(log_writer_thread_key, log_writer, &log); srv_threads.m_log_checkpointer.start(); srv_threads.m_log_flush_notifier.start(); srv_threads.m_log_flusher.start(); srv_threads.m_log_write_notifier.start(); srv_threads.m_log_writer....
select thread_id,name,type from performance_schema.threads where name like '%innodb%' group by name; master thread IO thread read/write thread insert buffer thread log io thread lock monitor thread error monitor thread purge thread page cleaner thread master thread (主线程)的线程优先级最高 其...
background master thread periodically. If the log writer threads are active, this function writes nothing. */voidlog_buffer_sync_in_background(){log_t&log= *log_sys;/* Just to be sure not to miss advance */log.recent_closed.advance_tail();/* If the log flusher thread is working, n...
log.buf_ready_for_write_lsn 这个lsn 主要是由于redo log 引入的concurrent writes 才引进的, 也就是log recent written buffer. 也就是到了这个lsn 为止, 之前的log buffer 里面都不会有空洞, 这个值也是由 log writer thread 来更新 log.flushed_to_disk_lsn ...
innodb_write_io_threads:该参数设置InnoDB数据库中负责将脏页同步到磁盘上的线程数量。innodb_write_io_threads的建议值为CPU的内核数量。 innodb_read_ahead_threshold:该参数表示InnoDB引擎中的顺序预读阀值。在buffer pool中的page也有一个组织结构:64个page组成一个extent结构。当InnoDB发现在一个extent结构中**已经...
Enables dedicated log writer threads for writing redo log records from the log buffer to the system buffers and flushing the system buffers to the redo log files. Dedicated log writer threads can improve performance on high-concurrency systems, but for low-concurrency systems, disabling dedicated lo...
innodb_flush_log_at_trx_commit:控制日志刷新到磁盘的策略,可以设置为0、1或2,不同的值对应不同的刷新频率和持久性保证。 innodb_max_dirty_pages_pct:设置Buffer Pool中脏页的最大比例,当脏页比例超过这个值时,Master Thread会更频繁地刷新脏页到磁盘。
注:三行挂起读写线程、缓冲池线程、日志线程的统计信息的值是检测I/O受限的应用的一个好方法,如果这些I/O大部分有挂起操作,那么负载可能I/O受限。在linux系统下使用参数:innodb_read_io_threads和innodb_write_io_threads两个变量来配置读写线程的数量,默认为各4个线程。
redo日志是存在于磁盘上的文件,包括ib_logfile0和ib_logfile1两个文件,常用于在crash恢复发生时将还没来得及写入到数据文件中但已经完成提交的事务在数据库初始化时重新执行一遍InnoDB对redo log buffer写入到redo log文件的方式提供了组提交(group commit)的方式,意味着针对一次写磁盘操作可以包含多个事务数据,用此方法...