LGRP_LATENCY(3LGRP) Locality Group Library Functions LGRP_LATENCY(3LGRP)
NAME
lgrp_latency, lgrp_latency_cookie - get latency between two lgroups
SYNOPSIS
cc [
flag... ]
file...
-llgrp [
library... ]
#include <sys/lgrp_user.h>
int lgrp_latency_cookie(
lgrp_cookie_t cookie,
lgrp_id_t from,
lgrp_id_t to,
lgrp_lat_between_t between);
int lgrp_latency(
lgrp_id_t from,
lgrp_id_t to);
DESCRIPTION
The
lgrp_latency_cookie() function takes a cookie representing a
snapshot of the lgroup hierarchy obtained from
lgrp_init(3LGRP) and
returns the latency value between a hardware resource in the
from lgroup to a hardware resource in the
to lgroup. If
from is the same
lgroup as
to, the latency value within that lgroup is returned.
The
between argument should be set to the following value to specify
between which hardware resources the latency should be measured:
LGRP_LAT_CPU_TO_MEM /* latency from CPU to memory */
The latency value is defined by the operating system and is platform-
specific. It can be used only for relative comparison of lgroups on
the running system. It does not necessarily represent the actual
latency between hardware devices, and it might not be applicable
across platforms.
The
lgrp_latency() function is similar to the
lgrp_latency_cookie() function, but returns the latency between the given lgroups at the
given instant in time. Since lgroups can be freed and reallocated,
this function might not be able to provide a consistent answer across
calls. For that reason, the
lgrp_latency_cookie() function should be
used in its place.
RETURN VALUES
Upon successful completion, the latency value is returned. Otherwise
-1 is returned and
errno is set to indicate the error.
ERRORS
The
lgrp_latency_cookie() and
lgrp_latency() functions will fail if:
EINVAL The specified cookie, lgroup ID, or value given for the
between argument is not valid.
ESRCH The specified lgroup ID was not found, the
from lgroup does
not contain any CPUs, or the
to lgroup does not have any
memory.
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_init(3LGRP),
lgrp_parents(3LGRP),
liblgrp(3LIB),
attributes(7) April 9, 2016 LGRP_LATENCY(3LGRP)
