man3/__ppc_set_ppr_med.3

   1 .\" Copyright (c) 2015, 2016 IBM Corporation.
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .TH __PPC_SET_PPR_MED 3 2021-03-22 "GNU C Library" "Linux\
   6 Programmer's Manual"
   7 .SH NAME
   8 __ppc_set_ppr_med, __ppc_set_ppr_very_low, __ppc_set_ppr_low, __ppc_set_ppr_med_low, __ppc_set_ppr_med_high \-
   9 Set the Program Priority Register
  10 .SH LIBRARY
  11 Standard C library
  12 .RI ( libc ", " \-lc )
  13 .SH SYNOPSIS
  14 .nf
  15 .B #include <sys/platform/ppc.h>
  16 .PP
  17 .B void __ppc_set_ppr_med(void);
  18 .B void __ppc_set_ppr_very_low(void);
  19 .B void __ppc_set_ppr_low(void);
  20 .B void __ppc_set_ppr_med_low(void);
  21 .B void __ppc_set_ppr_med_high(void);
  22 .fi
  23 .SH DESCRIPTION
  24 These functions provide access to the
  25 .I Program Priority Register
  26 (PPR) on the Power architecture.
  27 .PP
  28 The PPR is a 64-bit register that controls the program's priority.
  29 By adjusting the PPR value the programmer may improve system
  30 throughput by causing system resources to be used more
  31 efficiently, especially in contention situations.
  32 The available unprivileged states are covered by the following functions:
  33 .IP * 3
  34 .BR __ppc_set_ppr_med ()
  35 sets the Program Priority Register value to
  36 .I medium
  37 (default).
  38 .IP *
  39 .BR __ppc_set_ppr_very_low ()
  40 sets the Program Priority Register value to
  41 .IR "very low" .
  42 .IP *
  43 .BR __ppc_set_ppr_low ()
  44 sets the Program Priority Register value to
  45 .IR low .
  46 .IP *
  47 .BR __ppc_set_ppr_med_low ()
  48 sets the Program Priority Register value to
  49 .IR "medium low" .
  50 .PP
  51 The privileged state
  52 .I medium high
  53 may also be set during certain time intervals by problem-state (unprivileged)
  54 programs, with the following function:
  55 .IP * 3
  56 .BR __ppc_set_ppr_med_high ()
  57 sets the Program Priority to
  58 .IR "medium high" .
  59 .PP
  60 If the program priority is medium high when the time interval expires or if an
  61 attempt is made to set the priority to medium high when it is not allowed, the
  62 priority is set to medium.
  63 .SH VERSIONS
  64 The functions
  65 .BR __ppc_set_ppr_med (),
  66 .BR __ppc_set_ppr_low (),
  67 and
  68 .BR __ppc_set_ppr_med_low ()
  69 are provided by glibc since version 2.18.
  70 The functions
  71 .BR __ppc_set_ppr_very_low ()
  72 and
  73 .BR __ppc_set_ppr_med_high ()
  74 first appeared in glibc in version 2.23.
  75 .SH ATTRIBUTES
  76 For an explanation of the terms used in this section, see
  77 .BR attributes (7).
  78 .ad l
  79 .nh
  80 .TS
  81 allbox;
  82 lbx lb lb
  83 l l l.
  84 Interface       Attribute       Value
  85 T{
  86 .BR __ppc_set_ppr_med (),
  87 .BR __ppc_set_ppr_very_low (),
  88 .BR __ppc_set_ppr_low (),
  89 .BR __ppc_set_ppr_med_low (),
  90 .BR __ppc_set_ppr_med_high ()
  91 T}      Thread safety   MT-Safe
  92 .TE
  93 .hy
  94 .ad
  95 .sp 1
  96 .SH CONFORMING TO
  97 These functions are nonstandard GNU extensions.
  98 .SH NOTES
  99 The functions
 100 .BR __ppc_set_ppr_very_low ()
 101 and
 102 .BR __ppc_set_ppr_med_high ()
 103 will be defined by
 104 .I <sys/platform/ppc.h>
 105 if
 106 .B _ARCH_PWR8
 107 is defined.
 108 Availability of these functions can be tested using
 109 .BR "#ifdef _ARCH_PWR8" .
 110 .SH SEE ALSO
 111 .BR __ppc_yield (3)
 112 .PP
 113 .I Power ISA, Book\~II - Section\ 3.1 (Program Priority Registers)