简单记录
如下线面3种ID到底什么意思，这个问题我一直没去看：
(root@localhost)[05:47:31] [performance_schema ;]> select THREAD_ID,PROCESSLIST_ID,THREAD_OS_ID from performance_schema.threads ; +-----------+----------------+--------------+| THREAD_ID | PROCESSLIST_ID | THREAD_OS_ID |+-----------+----------------+--------------+| 1 | NULL | 17721 || 2 | NULL | 17728 || 3 | NULL | 17729 || 4 | NULL | 17730 || 5 | NULL | 17731 || 6 | NULL | 17732 || 7 | NULL | 17733 || 8 | NULL | 17734 || 9 | NULL | 17735 || 10 | NULL | 17736 || 11 | NULL | 17737 || 12 | NULL | 17738 || 13 | NULL | 17739 || 15 | NULL | 17743 || 16 | NULL | 17744 || 17 | NULL | 17745 || 18 | NULL | 17746 || 19 | NULL | 17747 || 20 | NULL | 17749 || 21 | NULL | 17748 || 22 | NULL | 17750 || 23 | NULL | 17751 || 24 | NULL | 17752 || 25 | NULL | 17763 || 26 | 1 | 17764 || 27 | 2 | 17969 || 44 | 19 | 31424 |+-----------+----------------+--------------+
PFS_thread* create_thread(PFS_thread_class *klass, const void *identity,
ulonglong processlist_id){
PFS_thread *pfs;
pfs_dirty_state dirty_state;
pfs= global_thread_container.allocate(& dirty_state); if (pfs != NULL)
{
pfs->m_thread_internal_id=
PFS_atomic::add_u64(&thread_internal_id_counter.m_u64, 1);
pfs->m_parent_thread_internal_id= 0;
pfs->m_processlist_id= static_cast<ulong>(processlist_id);
作者微信：gaopp_22389860
thread_internal_id_counter计数器一直增加。可以看到这是performance_schema内部使用的。
是传入参数processlist_id，也就是我们平时show processlist出来的。一般MySQL层使用它。
OS级别的线程ID，来自函数
pfs->m_thread_os_id= my_thread_os_id();
记录于此 以备后用。
作者微信：gaopp_22389860
