xref: /freebsd/lib/libkvm/kvm_getpcpu.3 (revision cd11f01e4a0022cf28cc3c8b80f58c2e91b44d27)

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.Dd August 19, 2008
.Dt KVM_GETPCPU 3
.Os
.Sh NAME
.Nm kvm_getmaxcpu ,
.Nm kvm_getpcpu
.Nd access per-CPU data
.Sh LIBRARY
.Lb libkvm
.Sh SYNOPSIS
.In sys/param.h
.In sys/pcpu.h
.In sys/sysctl.h
.In kvm.h
.Ft int
.Fn kvm_getmaxcpu "kvm_t *kd"
.Ft void *
.Fn kvm_getpcpu "kvm_t *kd" "int cpu"
.Sh DESCRIPTION
The
.Fn kvm_getmaxcpu
and
.Fn kvm_getpcpu
functions are used to access the per-CPU data of active processors in the
kernel indicated by
.Fa kd .
The
.Fn kvm_getmaxcpu
function returns the maximum number of CPUs supported by the kernel.
The
.Fn kvm_getpcpu
function returns a buffer holding the per-CPU data for a single CPU.
This buffer is described by the
.Vt "struct pcpu"
type.
The caller is responsible for releasing the buffer via a call to
.Xr free 3
when it is no longer needed.
If
.Fa cpu
is not active, then
.Dv NULL
is returned instead.
.Sh CACHING
These functions cache the nlist values for various kernel variables which are
reused in successive calls.
You may call either function with
.Fa kd
set to
.Dv NULL
to clear this cache.
.Sh RETURN VALUES
On success, the
.Fn kvm_getmaxcpu
function returns the maximum number of CPUs supported by the kernel.
If an error occurs,
it returns -1 instead.
.Pp
On success, the
.Fn kvm_getpcpu
function returns a pointer to an allocated buffer or
.Dv NULL.
If an error occurs,
it returns -1 instead.
.Pp
If either function encounters an error,
then an error message may be retrieved via
.Xr kvm_geterr 3.
.Sh SEE ALSO
.Xr free 3 ,
.Xr kvm 3