thread_stack in my.cnf

thread_stack is the per-connection stack size. It matters when stored programs, deep views, or pathological expression trees overflow the stack.

Floor

[mysqld]
thread_stack = 256K

Raise carefully: each connection reserves stack. Thousands of connections × oversized stacks is real RAM.

Not a performance lever

It does not speed queries, replace indexes, or substitute for max_allowed_packet / buffer pool tuning. It prevents a class of crashes.

Prefer fixing causes

• Shallower stored-program recursion
• Simpler views
• Less monstrous generated SQL

Set a known-good value for your version, watch for stack crashes after upgrades, then leave it alone.