xref: /freebsd/lib/libpmc/pmc_read.3 (revision 1c05a6ea6b849ff95e539c31adea887c644a6a01)
1.\" Copyright (c) 2007 Joseph Koshy.  All rights reserved.
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24.\" $FreeBSD$
25.\"
26.Dd November 25, 2007
27.Dt PMC_READ 3
28.Os
29.Sh NAME
30.Nm pmc_read ,
31.Nm pmc_rw ,
32.Nm pmc_write
33.Nd read and write hardware performance counters
34.Sh LIBRARY
35.Lb libpmc
36.Sh SYNOPSIS
37.In pmc.h
38.Ft int
39.Fn pmc_read "pmc_id_t pmc" "pmc_value_t *value"
40.Ft int
41.Fn pmc_rw "pmc_id_t pmc" "pmc_value_t newvalue" "pmc_value_t *oldvaluep"
42.Ft int
43.Fn pmc_write "pmc_id_t pmc" "pmc_value_t value"
44.Sh DESCRIPTION
45These functions read and write the current value of a PMC.
46.Pp
47Function
48.Fn pmc_read
49will read the current value of the PMC specified by argument
50.Fa pmc
51and write it to the location specified by argument
52.Fa value .
53.Pp
54Function
55.Fn pmc_write
56will set the current value of the PMC specified by argument
57.Fa pmc
58to the value specified by argument
59.Fa value .
60.Pp
61Function
62.Fn pmc_rw
63combines a read and a write into a single atomic operation.
64.Pp
65For write operations the PMC should be a quiescent state.
66.Sh RETURN VALUES
67.Rv -std
68.Sh ERRORS
69A call to these functions may fail with the following errors:
70.Bl -tag -width Er
71.It Bq Er EBUSY
72A write operation specified a currently running PMC.
73.It Bq Er EINVAL
74Argument
75.Fa pmc
76specified a PMC not in a readable state.
77.It Bq Er EINVAL
78The PMC specified by argument
79.Fa pmc
80was not owned by the current process.
81.El
82.Sh SEE ALSO
83.Xr pmc 3 ,
84.Xr hwpmc 4
85