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