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
* __ppc_set_ppr_very_low() sets the Program Priority Register value to
* __ppc_set_ppr_low() sets the Program Priority Register value to low.
* __ppc_set_ppr_med_low() sets the Program Priority Register value to
The privileged state medium high may also be set during certain time
intervals by problem-state (unprivileged) programs, with the following
* __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.
The functions __ppc_set_ppr_med(), __ppc_set_ppr_low() and
__ppc_set_ppr_med_low() are provided by glibc since version 2.18. The
functions __ppc_set_ppr_very_low() and __ppc_set_ppr_med_high() first
appeared in glibc in version 2.23.
For an explanation of the terms used in this section, see
|Interface | Attribute | Value |
Power ISA, Book II - Section 3.1 (Program Priority Registers)
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latest version of this page, can be found at
GNU C Library 2015-12-05 __PPC_SET_PPR_MED(3)
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