41        other constraints.  Processor binding and processor sets can restrict
  42        which lgroups a thread can run on, but do not change the lgroup
  43        affinities.
  44 
  45 
  46        Each thread can have an affinity for an lgroup in the system such that
  47        the thread will tend to be scheduled to run on that lgroup and allocate
  48        memory from there whenever possible.  If the thread has affinity for
  49        more than one lgroup, the operating system will try to run the thread
  50        and allocate its memory on the lgroup for which it has the strongest
  51        affinity, then the next strongest, and so on up through some small,
  52        system-dependent number of these lgroup affinities.  When multiple
  53        lgroups have the same affinity, the order of preference among them is
  54        unspecified and up to the operating system to choose.  The lgroup with
  55        the strongest affinity that the thread can run on is known as its "home
  56        lgroup" (see lgrp_home(3LGRP)) and is usually the operating system's
  57        first choice of where to run the thread and allocate its memory.
  58 
  59 
  60         There are different levels of affinity that can be specified by a
  61        thread for a particuliar lgroup.  The levels of affinity are the
  62        following from strongest to weakest:
  63 
  64          LGRP_AFF_STRONG         /* strong affinity */
  65          LGRP_AFF_WEAK           /* weak affinity */
  66          LGRP_AFF_NONE           /* no affinity */
  67 
  68 
  69 
  70        The LGRP_AFF_STRONG affinity serves as a hint to the operating system
  71        that the calling thread has a strong affinity for the given lgroup.  If
  72        this is the thread's home lgroup, the operating system will avoid
  73        rehoming it to another lgroup if possible.  However, dynamic
  74        reconfiguration, processor offlining, processor binding, and processor
  75        set binding and manipulation are examples of events that can cause the
  76        operating system to change the thread's home lgroup for which it has a
  77        strong affinity.
  78 
  79 
  80        The LGRP_AFF_WEAK affinity is a hint to the operating system that the
  81        calling thread has a weak affinity for the given lgroup.  If a thread
  82        has a weak affinity for its home lgroup, the operating system interpets
  83        this to mean that thread does not mind whether it is rehomed, unlike
  84        LGRP_AFF_STRONG.  Load balancing, dynamic reconfiguration, processor
  85        binding, or processor set binding and manipulation are examples of
  86        events that can cause the operating system to change a thread's home
  87        lgroup for which it has a weak affinity.
  88 
  89 
  90        The LGRP_AFF_NONE affinity signifies no affinity and can be used to
  91        remove a thread's affinity for a particuliar lgroup.  Initially, each
  92        thread has no affinity to any lgroup.  If a thread has no lgroup
  93        affinities set, the operating system chooses a home lgroup for the
  94        thread with no affinity set.
  95 
  96 RETURN VALUES
  97        Upon successful completion, lgrp_affinity_get() returns the affinity
  98        for the given lgroup.
  99 
 100 
 101        Upon successful completion, lgrp_affinity_set() return 0.
 102 
 103 
 104        Otherwise, both functions return -1 and set errno to indicate the
 105        error.
 106 
 107 ERRORS
 108        The lgrp_affinity_get() and lgrp_affinity_set() functions will fail if:
 109 
 110        EINVAL
 111                  The specified lgroup, affinity, or ID type is not valid.

  41        other constraints.  Processor binding and processor sets can restrict
  42        which lgroups a thread can run on, but do not change the lgroup
  43        affinities.
  44 
  45 
  46        Each thread can have an affinity for an lgroup in the system such that
  47        the thread will tend to be scheduled to run on that lgroup and allocate
  48        memory from there whenever possible.  If the thread has affinity for
  49        more than one lgroup, the operating system will try to run the thread
  50        and allocate its memory on the lgroup for which it has the strongest
  51        affinity, then the next strongest, and so on up through some small,
  52        system-dependent number of these lgroup affinities.  When multiple
  53        lgroups have the same affinity, the order of preference among them is
  54        unspecified and up to the operating system to choose.  The lgroup with
  55        the strongest affinity that the thread can run on is known as its "home
  56        lgroup" (see lgrp_home(3LGRP)) and is usually the operating system's
  57        first choice of where to run the thread and allocate its memory.
  58 
  59 
  60        There are different levels of affinity that can be specified by a
  61        thread for a particular lgroup.  The levels of affinity are the
  62        following from strongest to weakest:
  63 
  64          LGRP_AFF_STRONG         /* strong affinity */
  65          LGRP_AFF_WEAK           /* weak affinity */
  66          LGRP_AFF_NONE           /* no affinity */
  67 
  68 
  69 
  70        The LGRP_AFF_STRONG affinity serves as a hint to the operating system
  71        that the calling thread has a strong affinity for the given lgroup.  If
  72        this is the thread's home lgroup, the operating system will avoid
  73        rehoming it to another lgroup if possible.  However, dynamic
  74        reconfiguration, processor offlining, processor binding, and processor
  75        set binding and manipulation are examples of events that can cause the
  76        operating system to change the thread's home lgroup for which it has a
  77        strong affinity.
  78 
  79 
  80        The LGRP_AFF_WEAK affinity is a hint to the operating system that the
  81        calling thread has a weak affinity for the given lgroup.  If a thread
  82        has a weak affinity for its home lgroup, the operating system interpets
  83        this to mean that thread does not mind whether it is rehomed, unlike
  84        LGRP_AFF_STRONG.  Load balancing, dynamic reconfiguration, processor
  85        binding, or processor set binding and manipulation are examples of
  86        events that can cause the operating system to change a thread's home
  87        lgroup for which it has a weak affinity.
  88 
  89 
  90        The LGRP_AFF_NONE affinity signifies no affinity and can be used to
  91        remove a thread's affinity for a particular lgroup.  Initially, each
  92        thread has no affinity to any lgroup.  If a thread has no lgroup
  93        affinities set, the operating system chooses a home lgroup for the
  94        thread with no affinity set.
  95 
  96 RETURN VALUES
  97        Upon successful completion, lgrp_affinity_get() returns the affinity
  98        for the given lgroup.
  99 
 100 
 101        Upon successful completion, lgrp_affinity_set() return 0.
 102 
 103 
 104        Otherwise, both functions return -1 and set errno to indicate the
 105        error.
 106 
 107 ERRORS
 108        The lgrp_affinity_get() and lgrp_affinity_set() functions will fail if:
 109 
 110        EINVAL
 111                  The specified lgroup, affinity, or ID type is not valid.