Re: 1135 Can't create a new thread (errno 11)...

[Tijl Deneut]

I think I found the main problem:
CentOS (only version 6?) by default has a restriction on the max. user processes (enforce by the file /etc/security/limits.d/90-nproc.conf) from 7820 processes to 1024 (per program, mysql included).

The reason for this, imho, is to be protected against fork bombs.

When you perform too much concurrent user threads after each other, this becomes a problem (errno 11).
This means: when you perform a test with concurrency 1100 it is no problem, but if you try 1000 followed by 1100. There is a problem.

One side note: it seems that when you reboot the machine, the 'nproc'-restriction only gets enforced *after* the start of the 'mysqld'-process. This means that, after a reboot, as long as the mysql-server runs, there is no problem. But if you restart the server, then it suffers from the nproc-enforcement.

Do you think I could be correct?