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28.Dd June 2, 2016
29.Dt PTHREAD_ATTR_AFFINITY_NP 3
30.Os
31.Sh NAME
32.Nm pthread_attr_getaffinity_np ,
33.Nm pthread_attr_setaffinity_np
34.Nd manage CPU affinity in thread attribute objects
35.Sh LIBRARY
36.Lb libpthread
37.Sh SYNOPSIS
38.In pthread_np.h
39.Ft int
40.Fn pthread_attr_getaffinity_np "const pthread_attr_t *pattr" "size_t cpusetsize" "cpuset_t *cpusetp"
41.Ft int
42.Fn pthread_attr_setaffinity_np "pthread_attr_t *pattr" "size_t cpusetsize" "const cpuset_t *cpusetp"
43.Sh DESCRIPTION
44The
45.Fn pthread_attr_getaffinity_np
46and
47.Fn pthread_attr_setaffinity_np
48functions allow the manipulation of sets of CPUs available to the specified thread attribute object.
49.Pp
50Masks of type
51.Ft cpuset_t
52are composed using the
53.Dv CPU_SET
54macros.
55The kernel tolerates large sets as long as all CPUs specified
56in the set exist.
57Sets smaller than the kernel uses generate an error on calls to
58.Fn pthread_attr_getaffinity_np
59even if the result set would fit within the user supplied set.
60Calls to
61.Fn pthread_attr_setaffinity_np
62tolerate small sets with no restrictions.
63.Pp
64The supplied mask should have a size of
65.Fa cpusetsize
66bytes.
67This size is usually provided by calling
68.Li sizeof(cpuset_t)
69which is ultimately determined by the value of
70.Dv CPU_SETSIZE
71as defined in
72.In sys/cpuset.h .
73.Pp
74.Fn pthread_attr_getaffinity_np
75retrieves the
76mask from the thread attribute object specified by
77.Fa pattr ,
78and stores it in the space provided by
79.Fa cpusetp .
80.Pp
81.Fn pthread_attr_setaffinity_np
82sets the mask for the thread attribute object specified by
83.Fa pattr
84to the value in
85.Fa cpusetp .
86.Sh RETURN VALUES
87If successful, the
88.Fn pthread_attr_getaffinity_np
89and
90.Fn pthread_attr_setaffinity_np
91functions will return zero.
92Otherwise an error number will be returned
93to indicate the error.
94.Sh ERRORS
95The
96.Fn pthread_attr_getaffinity_np
97functions will fail if:
98.Bl -tag -width Er
99.It Bq Er EINVAL
100The
101.Fa pattr
102or the attribute specified by it is
103.Dv NULL .
104.It Bq Er ERANGE
105The
106.Fa cpusetsize
107is too small.
108.El
109.Pp
110The
111.Fn pthread_attr_setaffinity_np
112function will fail if:
113.Bl -tag -width Er
114.It Bq Er EINVAL
115The
116.Fa pattr
117or the attribute specified by it is
118.Dv NULL .
119.It Bq Er EINVAL
120The
121.Fa cpusetp
122specified a CPU that was outside the set supported by the kernel.
123.It Bq Er ERANGE
124The
125.Fa cpusetsize
126is too small.
127.It Bq Er ENOMEM
128Insufficient memory exists to store the cpuset mask.
129.El
130.Sh SEE ALSO
131.Xr cpuset 1 ,
132.Xr cpuset 2 ,
133.Xr cpuset_getid 2 ,
134.Xr cpuset_setid 2 ,
135.Xr pthread_getaffinity_np 3 ,
136.Xr pthread_setaffinity_np 3
137.Sh STANDARDS
138The
139.Nm pthread_attr_getaffinity_np
140and
141.Nm pthread_attr_setaffinity_np
142functions are non-standard
143.Fx
144extensions and may be not available on other operating systems.
145.Sh HISTORY
146The
147.Nm pthread_attr_getaffinity_np
148and
149.Nm pthread_attr_setaffinity_np
150functions first appeared in
151.Fx 7.2 .
152.Sh AUTHORS
153.An -nosplit
154The
155.Nm pthread_attr_getaffinity_np
156and
157.Nm pthread_attr_setaffinity_np
158functions were written by
159.An David Xu Aq Mt davidxu@FreeBSD.org ,
160and this manpage was written by
161.An Xin LI Aq Mt delphij@FreeBSD.org .
162