Alibaba Cloud Linux:What do I do if -ENOMEM errors occur during io_uring creation?

Cause

• When the system's physical memory is insufficient, the kernel cannot allocate the required memory for io_uring initialization or operation.

• During an io_uring instance's creation, the kernel requests locked memory pages. Even with sufficient total system memory, a low locked memory limit may still result in an -ENOMEM error.

  Run the following command to view the available memory for the current user:

  ulimit -a

  The following command output is returned.

  

  max locked memory is the maximum available locked memory for the user. Locked memory refers to memory pages marked as non-swappable to disks and is used in scenarios that require high performance and low latency.

Solution

Run the target program with root privileges to bypass the lock_memory limits.

• For user-purchased Elastic Compute Service (ECS) instances, run the sudo command to escalate to root administrator privileges and run the target program.

• In container scenarios, check whether the container startup parameters include administrator privileges.

  For example, even when you run the programs as root in a Docker container, errors may still occur if you do not configure the --privileged=true setting. This prevents the container's root user from fully inheriting the host's root privileges.

  Warning

  --privileged=true grants the container nearly all host privileges. Proceed with caution.

Cause

io_uring allocates memory for the submission queue (SQ) and completion queue (CQ) during initialization. A large queue depth (entries) can exhaust available memory.

Solution

Configure appropriate and reasonable io_uring queue depths.

Avoid specifying excessively large entries values. The io_uring_queue_init and io_uring_queue_init_params interfaces in liburing are used to create io_uring instances. Specify the entries parameters within the allowed memory range.

int io_uring_queue_init(unsigned entries,
                       struct io_uring *ring,
                       unsigned flags)
int io_uring_queue_init_params(unsigned entries,
                              struct io_uring *ring,
                              struct io_uring_params *params);

sudo yum install liburing -y
man io_uring_queue_init