---
name: "io_uring_register_iowq_max_workers"
section: "3"
platform: "linux"
package: "liburing"
version: "2.15-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_uring_register_iowq_max_workers"
---

# io\_uring\_register\_iowq\_max\_workers(3)

modify the maximum allowed async workers

## NAME

io\_uring\_register\_iowq\_max\_workers - modify the maximum allowed async workers

## SYNOPSIS

```
#include <liburing.h>
```

**int io\_uring\_register\_iowq\_max\_workers(struct io\_uring \****ring***,**                                        **unsigned int \****values***);**

## DESCRIPTION

io\_uring async workers are split into two types:

- **Bounded**

  These workers have a bounded execution time. Examples of that are filesystem reads, which normally complete in a relatively short amount of time. In case of disk failures, they are still bounded by a timeout operation that will abort them if exceeded.

- **Unbounded**

  Work items here may take an indefinite amount of time to complete. Examples include doing IO to sockets, pipes, or any other non-regular type of file.

By default, the amount of bounded IO workers is limited to how many SQ entries the ring was setup with, or 4 times the number of online CPUs in the system, whichever is smaller. Unbounded workers are only limited by the process task limit, as indicated by the rlimit **RLIMIT\_NPROC** limit.

This can be modified by calling **io\_uring\_register\_iowq\_max\_workers** with *ring* set to the ring in question, and *values* pointing to an array of two values. The first element should contain the number of desired bounded workers, and the second element should contain the number of desired unbounded workers. These are both maximum values, io\_uring will not maintain a high count of idle workers, they are reaped when they are not necessary anymore.

If called with both values set to 0, the existing values are returned.

## RETURN VALUE

Returns **0** on success, with *values* containing the previous values for the settings. On error, any of the following may be returned.

- **-EFAULT**

  The kernel was unable to copy the memory pointer to by *values* as it was invalid.

- **-EINVAL**

  *values* was **NULL** or the new values exceeded the maximum allowed value.

## SEE ALSO

[**io\_uring\_queue\_init**(3)](/io_uring_queue_init/3.md), [**io\_uring\_register**(2)](/io_uring_register/2.md)