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man pages section 3: Extended Library Functions, Volume 2

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Updated: Friday, August 13, 2021



lgrp_init - initialize lgroup interface


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

lgrp_cookie_t lgrp_init(lgrp_view_t view);


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 hierarchy 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 hierarchy 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.


The lgrp_init() function will fail if:


The view is not valid.


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


There is not enough memory available to allocate the snapshot of the lgroup hierarchy, but the application could try again later.

The lgrp_init() function may also set errno values as described by pset_bind(2).


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

Interface Stability

See Also

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