---
name: "sched_rr_get_interval"
section: "2"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/sched_rr_get_interval"
---

# sched\_rr\_get\_interval(2)

get the SCHED\_RR interval for the named process

## NAME

sched\_rr\_get\_interval - get the SCHED\_RR interval for the named process

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <sched.h>
```

**int sched\_rr\_get\_interval(pid\_t** *pid***, struct timespec \****tp***);**

## DESCRIPTION

**sched\_rr\_get\_interval**() writes into the [**timespec**(3)](/timespec/3.md) structure pointed to by *tp* the round-robin time quantum for the process identified by *pid*. The specified process should be running under the **SCHED\_RR** scheduling policy.

If *pid* is zero, the time quantum for the calling process is written into *\*tp*.

## RETURN VALUE

On success, **sched\_rr\_get\_interval**() returns 0. On error, -1 is returned, and *errno* is set to indicate the error.

## ERRORS

- **EFAULT**

  Problem with copying information to user space.

- **EINVAL**

  Invalid *pid*.

- **ENOSYS**

  The system call is not yet implemented (only on rather old kernels).

- **ESRCH**

  Could not find a process with the ID *pid*.

## VERSIONS

### Linux

Linux 3.9 added a new mechanism for adjusting (and viewing) the **SCHED\_RR** quantum: the */proc/sys/kernel/sched\_rr\_timeslice\_ms* file exposes the quantum as a millisecond value, whose default is 100. Writing 0 to this file resets the quantum to the default value.

## STANDARDS

POSIX.1-2024.

## HISTORY

POSIX.1-2001.

### Linux

POSIX does not specify any mechanism for controlling the size of the round-robin time quantum. Older Linux kernels provide a (nonportable) method of doing this. The quantum can be controlled by adjusting the process's nice value (see [**setpriority**(2)](/setpriority/2.md)). Assigning a negative (i.e., high) nice value results in a longer quantum; assigning a positive (i.e., low) nice value results in a shorter quantum. The default quantum is 0.1 seconds; the degree to which changing the nice value affects the quantum has varied somewhat across kernel versions. This method of adjusting the quantum was removed starting with Linux 2.6.24.

## NOTES

POSIX systems on which **sched\_rr\_get\_interval**() is available define **\_POSIX\_PRIORITY\_SCHEDULING** in *\<unistd.h\>*.

## SEE ALSO

[**timespec**(3)](/timespec/3.md), [**sched**(7)](/sched/7.md)