---
name: "__ppc_set_ppr_med"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/__ppc_set_ppr_med"
---

# \_\_ppc\_set\_ppr\_med(3)

Set the Program Priority Register

Programmer's Manual"

## NAME

\_\_ppc\_set\_ppr\_med, \_\_ppc\_set\_ppr\_very\_low, \_\_ppc\_set\_ppr\_low, \_\_ppc\_set\_ppr\_med\_low, \_\_ppc\_set\_ppr\_med\_high - Set the Program Priority Register

## LIBRARY

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

## SYNOPSIS

```
#include <sys/platform/ppc.h>
```

**void \_\_ppc\_set\_ppr\_med(void);** **void \_\_ppc\_set\_ppr\_very\_low(void);** **void \_\_ppc\_set\_ppr\_low(void);** **void \_\_ppc\_set\_ppr\_med\_low(void);** **void \_\_ppc\_set\_ppr\_med\_high(void);**

## DESCRIPTION

These functions provide access to the *Program Priority Register* (PPR) on the Power architecture.

The PPR is a 64-bit register that controls the program's priority. By adjusting the PPR value the programmer may improve system throughput by causing system resources to be used more efficiently, especially in contention situations. The available unprivileged states are covered by the following functions:

- **\_\_ppc\_set\_ppr\_med**()

  sets the Program Priority Register value to *medium* (default).

- **\_\_ppc\_set\_ppr\_very\_low**()

  sets the Program Priority Register value to *very low*.

- **\_\_ppc\_set\_ppr\_low**()

  sets the Program Priority Register value to *low*.

- **\_\_ppc\_set\_ppr\_med\_low**()

  sets the Program Priority Register value to *medium low*.

The privileged state *medium high* may also be set during certain time intervals by problem-state (unprivileged) programs, with the following function:

- **\_\_ppc\_set\_ppr\_med\_high**()

  sets the Program Priority to *medium high*.

If the program priority is medium high when the time interval expires or if an attempt is made to set the priority to medium high when it is not allowed, the priority is set to medium.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **\_\_ppc\_set\_ppr\_med**(), **\_\_ppc\_set\_ppr\_very\_low**(), **\_\_ppc\_set\_ppr\_low**(), **\_\_ppc\_set\_ppr\_med\_low**(), **\_\_ppc\_set\_ppr\_med\_high**() | Thread safety | MT-Safe |

## STANDARDS

GNU.

## HISTORY

- **\_\_ppc\_set\_ppr\_med**() **\_\_ppc\_set\_ppr\_low**() **\_\_ppc\_set\_ppr\_med\_low**()

  glibc 2.18.

- **\_\_ppc\_set\_ppr\_very\_low**() **\_\_ppc\_set\_ppr\_med\_high**()

  glibc 2.23.

## NOTES

The functions **\_\_ppc\_set\_ppr\_very\_low**() and **\_\_ppc\_set\_ppr\_med\_high**() will be defined by *\<sys/platform/ppc.h\>* if **\_ARCH\_PWR8** is defined. Availability of these functions can be tested using **#ifdef \_ARCH\_PWR8**.

## SEE ALSO

[**\_\_ppc\_yield**(3)](/__ppc_yield/3.md)

*Power ISA, Book II - Section 3.1 (Program Priority Registers)*