MySQL Memory Monitor

The previous blog describes a case where memory spikes due to SQL query Information_schema tables.

Today, by the way, a THD memory is monitored:

Let's introduce the memory of MySQL:

1. In-thread memory: thd->mem_root, during the execution of SQL, the requested memory is allocated from Thd->mem_root and released at the end of SQL.

2. Out-of-thread memory: Object-specific mem_root; For example, table, table_share,st_transactions, etc. all have proprietary mem_root.

So: For SQL-induced memory spikes, you can monitor thd->mem_root changes. For others, such as temporary tables created, additional monitoring is required.

Add a thd_size field to the function called by sql/sql_show.cc show Processlist.

The final results are as follows: