aio-max-nr in general and “InnoDB: Error: io_setup() failed with EAGAIN” in particular

Август 3rd, 2012 | Posted by self in MariaDB

The problem many MySQL/MariaDB 5.5+ users are painfully aware of:

InnoDB: Using Linux native AIO
InnoDB: Warning: io_setup() failed with EAGAIN. Will make 5 attempts before giving up.
InnoDB: Warning: io_setup() attempt 1 failed.
InnoDB: Warning: io_setup() attempt 2 failed.
InnoDB: Warning: io_setup() attempt 3 failed.
InnoDB: Warning: io_setup() attempt 4 failed.
InnoDB: Warning: io_setup() attempt 5 failed.
InnoDB: Error: io_setup() failed with EAGAIN after 5 attempts.
InnoDB: You can disable Linux Native AIO by setting innodb_native_aio = off in my.cnf
InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: Completed initialization of buffer pool
mysqld got signal 11 ;

There is no news that disabling InnoDB native AIO is not exactly the best possible option. It’s also not a secret that the alternative is increasing aio-max-nr if possible. What is always news for me is how it’s done…
So,

to see the current value:
cat /proc/sys/fs/aio-max-nr
65536

to set the new one:
sudo sysctl fs.aio-max-nr=262144

And yeah, it has already been fixed in MariaDB: replication tests crash… But still.

Btw, while we are here — what is aio-max-nr, anyway?

aio-nr is the running total of the number of events specified on the io_setup system call for all currently active aio contexts. If aio-nr reaches aio-max-nr then io_setup will fail with EAGAIN. Note that raising aio-max-nr does not result in the pre-allocation or re-sizing of any kernel data structures.

Source: http://www.kernel.org/doc/Documentation/sysctl/fs.txt

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