LGRP_INIT(3LGRP) Locality Group Library Functions LGRP_INIT(3LGRP)

NAME

lgrp_init - initialize lgroup interface

SYNOPSIS

cc [ flag... ] file... -llgrp [ library... ]
#include <sys/lgrp_user.h>

lgrp_cookie_t lgrp_init(lgrp_view_t view);

DESCRIPTION

The lgrp_init() function initializes the lgroup interface and takes a
snapshot of the lgroup hierarchy with the given view. If the given view
is LGRP_VIEW_CALLER, the snapshot contains only the resources that are
available to the caller (for example, with respect to processor sets).
When the view is LGRP_VIEW_OS, the snapshot contains what is available to
the operating system.


Given the view, lgrp_init() returns a cookie representing this snapshot
of the lgroup hierarchy. This cookie should be used with other routines
in the lgroup interface needing the lgroup hierarchy. The
lgrp_fini(3LGRP) function should be called with the cookie when it is no
longer needed.


The lgroup hiearchy represents the latency topology of the machine. The
hierarchy is simplified to be a tree and can be used to find the nearest
resources.


The lgroup hiearchy consists of a root lgroup, which is the maximum
bounding locality group of the system, contains all the CPU and memory
resources of the machine, and may contain other locality groups that
contain CPUs and memory within a smaller locality. The leaf lgroups
contain resources within the smallest latency.


The resources of a given lgroup come directly from the lgroup itself or
from leaf lgroups contained within the lgroup. Leaf lgroups directly
contain their own resources and do not encapsulate any other lgroups.


The lgroup hierarchy can be used to find the nearest resources. From a
given lgroup, the closest resources can be found in the lgroup itself.
After that, the next nearest resources can be found in its parent lgroup,
and so on until the root lgroup is reached where all the resources of the
machine are located.

RETURN VALUES

Upon successful completion, lgrp_init() returns a cookie. Otherwise it
returns LGRP_COOKIE_NONE and sets errno to indicate the error.

ERRORS

The lgrp_init() function will fail if:

EINVAL
The view is not valid.


ENOMEM
There was not enough memory to allocate the snapshot of the
lgroup hierarchy.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Evolving |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

lgrp_children(3LGRP), lgrp_cookie_stale(3LGRP), lgrp_cpus(3LGRP),
lgrp_fini(3LGRP), lgrp_mem_size(3LGRP), lgrp_nlgrps(3LGRP),
lgrp_parents(3LGRP), lgrp_resources(3LGRP), lgrp_root(3LGRP),
lgrp_view(3LGRP), liblgrp(3LIB), attributes(7)

January 26, 2005 LGRP_INIT(3LGRP)