'\" te
.\" Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
.TH lgrp_device_lgrps 3LGRP "13 Mar 2012" "SunOS 5.11" "Locality Group Library Functions"
.SH NAME
lgrp_device_lgrps \- get IDs of lgroups closest to the specified I/O device
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag \&.\|.\|.\fR ] \fIfile\fR\&.\|.\|. \fB-llgrp\fR [ \fIlibrary \&.\|.\|.\fR ] 
#include <sys/lgrp_user.h>

\fBint\fR \fBlgrp_device_lgrps\fR(\fBchar *\fR\fIdevice_path\fR, \fBlgrp_id_t *\fR \fIlgrpids\fR,
     \fBuint_t\fR \fIcount\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBlgrp_device_lgrps()\fR returns the number of lgroups closest to the specified I/O device. If both \fIlgrpids\fR[] is non-null and \fIcount\fR is not 0, \fIlgrpids\fR[] is also filled up to the specified \fIcount\fR of lgroup IDs closest to the device.
.sp
.LP
Each I/O device on the system can be connected to one or more NUMA nodes. In order to optimize I/O performance for a given device through locality, an application needs to know which lgroups are closest to the I/O device and place its threads and/or memory needed for performing I/O near the device. It is therefore important for applications to know the NUMA I/O topology of the system.
.sp
.LP
The \fIdevice_path\fR parameter is the path to an I/O device specified by the caller.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBlgrp_device_lgrps()\fR returns the number of lgroups closest to the specified I/O device. Otherwise, it returns -1 and \fIerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBlgrp_device_lgrps()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEACCES\fR\fR
.ad
.RS 10n
.rt  
Operation permission is denied to the calling process (see \fBIntro\fR(2).
.RE

.sp
.ne 2
.mk
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 10n
.rt  
The \fIlgrpids\fR parameter points to an invalid memory address.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
An invalid device path is specified.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENOENT\fR\fR
.ad
.RS 10n
.rt  
The specified lgroup path does not name an existing device node.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBIntro\fR(2), \fBlgrp_affinity_get\fR(3LGRP), \fBlgrp_cpus\fR(3LGRP), \fBlgrp_nlgrps\fR(3LGRP), \fBlgrp_resources\fR(3LGRP), \fBliblgrp\fR(3LIB), \fBattributes\fR(5)