136 lines
7.6 KiB
Groff
136 lines
7.6 KiB
Groff
.TH "hwlocality_cpukinds" 3 "Wed Dec 14 2022" "Version 2.9.0" "Hardware Locality (hwloc)" \" -*- nroff -*-
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.ad l
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.nh
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.SH NAME
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hwlocality_cpukinds \- Kinds of CPU cores
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.SH SYNOPSIS
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.br
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.PP
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.SS "Functions"
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.in +1c
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.ti -1c
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.RI "int \fBhwloc_cpukinds_get_nr\fP (\fBhwloc_topology_t\fP topology, unsigned long flags)"
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.br
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.ti -1c
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.RI "int \fBhwloc_cpukinds_get_by_cpuset\fP (\fBhwloc_topology_t\fP topology, \fBhwloc_const_bitmap_t\fP cpuset, unsigned long flags)"
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.br
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.ti -1c
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.RI "int \fBhwloc_cpukinds_get_info\fP (\fBhwloc_topology_t\fP topology, unsigned kind_index, \fBhwloc_bitmap_t\fP cpuset, int *efficiency, unsigned *nr_infos, struct \fBhwloc_info_s\fP **infos, unsigned long flags)"
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.br
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.ti -1c
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.RI "int \fBhwloc_cpukinds_register\fP (\fBhwloc_topology_t\fP topology, \fBhwloc_bitmap_t\fP cpuset, int forced_efficiency, unsigned nr_infos, struct \fBhwloc_info_s\fP *infos, unsigned long flags)"
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.br
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.in -1c
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.SH "Detailed Description"
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.PP
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Platforms with heterogeneous CPUs may have some cores with different features or frequencies\&. This API exposes identical PUs in sets called CPU kinds\&. Each PU of the topology may only be in a single kind\&.
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.PP
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The number of kinds may be obtained with \fBhwloc_cpukinds_get_nr()\fP\&. If the platform is homogeneous, there may be a single kind with all PUs\&. If the platform or operating system does not expose any information about CPU cores, there may be no kind at all\&.
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.PP
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The index of the kind that describes a given CPU set (if any, and not partially) may be obtained with \fBhwloc_cpukinds_get_by_cpuset()\fP\&.
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.PP
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From the index of a kind, it is possible to retrieve information with \fBhwloc_cpukinds_get_info()\fP: an abstracted efficiency value, and an array of info attributes (for instance the 'CoreType' and 'FrequencyMaxMHz', see \fBCPU Kinds\fP)\&.
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.PP
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A higher efficiency value means greater intrinsic performance (and possibly less performance/power efficiency)\&. Kinds with lower efficiency values are ranked first: Passing 0 as \fCkind_index\fP to \fBhwloc_cpukinds_get_info()\fP will return information about the CPU kind with lower performance but higher energy-efficiency\&. Higher \fCkind_index\fP values would rather return information about power-hungry high-performance cores\&.
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.PP
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When available, efficiency values are gathered from the operating system\&. If so, \fCcpukind_efficiency\fP is set in the struct \fBhwloc_topology_discovery_support\fP array\&. This is currently available on Windows 10, Mac OS X (Darwin), and on some Linux platforms where core 'capacity' is exposed in sysfs\&.
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.PP
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If the operating system does not expose core efficiencies natively, hwloc tries to compute efficiencies by comparing CPU kinds using frequencies (on ARM), or core types and frequencies (on other architectures)\&. The environment variable HWLOC_CPUKINDS_RANKING may be used to change this heuristics, see \fBEnvironment Variables\fP\&.
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.PP
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If hwloc fails to rank any kind, for instance because the operating system does not expose efficiencies and core frequencies, all kinds will have an unknown efficiency (\fC-1\fP), and they are not indexed/ordered in any specific way\&.
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.SH "Function Documentation"
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.PP
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.SS "int hwloc_cpukinds_get_by_cpuset (\fBhwloc_topology_t\fP topology, \fBhwloc_const_bitmap_t\fP cpuset, unsigned long flags)"
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.PP
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Get the index of the CPU kind that contains CPUs listed in \fCcpuset\fP\&. \fCflags\fP must be \fC0\fP for now\&.
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.PP
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\fBReturns\fP
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.RS 4
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The index of the CPU kind (positive integer or 0) on success\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCEXDEV\fP if \fCcpuset\fP is only partially included in the some kind\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCENOENT\fP if \fCcpuset\fP is not included in any kind, even partially\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCEINVAL\fP if parameters are invalid\&.
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.RE
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.PP
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.SS "int hwloc_cpukinds_get_info (\fBhwloc_topology_t\fP topology, unsigned kind_index, \fBhwloc_bitmap_t\fP cpuset, int * efficiency, unsigned * nr_infos, struct \fBhwloc_info_s\fP ** infos, unsigned long flags)"
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.PP
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Get the CPU set and infos about a CPU kind in the topology\&. \fCkind_index\fP identifies one kind of CPU between 0 and the number of kinds returned by \fBhwloc_cpukinds_get_nr()\fP minus 1\&.
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.PP
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If not \fCNULL\fP, the bitmap \fCcpuset\fP will be filled with the set of PUs of this kind\&.
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.PP
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The integer pointed by \fCefficiency\fP, if not \fCNULL\fP will, be filled with the ranking of this kind of CPU in term of efficiency (see above)\&. It ranges from \fC0\fP to the number of kinds (as reported by \fBhwloc_cpukinds_get_nr()\fP) minus 1\&.
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.PP
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Kinds with lower efficiency are reported first\&.
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.PP
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If there is a single kind in the topology, its efficiency \fC0\fP\&. If the efficiency of some kinds of cores is unknown, the efficiency of all kinds is set to \fC-1\fP, and kinds are reported in no specific order\&.
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.PP
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The array of info attributes (for instance the 'CoreType', 'FrequencyMaxMHz' or 'FrequencyBaseMHz', see \fBCPU Kinds\fP) and its length are returned in \fCinfos\fP or \fCnr_infos\fP\&. The array belongs to the topology, it should not be freed or modified\&.
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.PP
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If \fCnr_infos\fP or \fCinfos\fP is \fCNULL\fP, no info is returned\&.
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.PP
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\fCflags\fP must be \fC0\fP for now\&.
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.PP
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\fBReturns\fP
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.RS 4
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\fC0\fP on success\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCENOENT\fP if \fCkind_index\fP does not match any CPU kind\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCEINVAL\fP if parameters are invalid\&.
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.RE
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.PP
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.SS "int hwloc_cpukinds_get_nr (\fBhwloc_topology_t\fP topology, unsigned long flags)"
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.PP
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Get the number of different kinds of CPU cores in the topology\&. \fCflags\fP must be \fC0\fP for now\&.
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.PP
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\fBReturns\fP
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.RS 4
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The number of CPU kinds (positive integer) on success\&.
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.PP
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\fC0\fP if no information about kinds was found\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCEINVAL\fP if \fCflags\fP is invalid\&.
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.RE
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.PP
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.SS "int hwloc_cpukinds_register (\fBhwloc_topology_t\fP topology, \fBhwloc_bitmap_t\fP cpuset, int forced_efficiency, unsigned nr_infos, struct \fBhwloc_info_s\fP * infos, unsigned long flags)"
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.PP
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Register a kind of CPU in the topology\&. Mark the PUs listed in \fCcpuset\fP as being of the same kind with respect to the given attributes\&.
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.PP
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\fCforced_efficiency\fP should be \fC-1\fP if unknown\&. Otherwise it is an abstracted efficiency value to enforce the ranking of all kinds if all of them have valid (and different) efficiencies\&.
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.PP
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The array \fCinfos\fP of size \fCnr_infos\fP may be used to provide info names and values describing this kind of PUs\&.
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.PP
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\fCflags\fP must be \fC0\fP for now\&.
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.PP
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Parameters \fCcpuset\fP and \fCinfos\fP will be duplicated internally, the caller is responsible for freeing them\&.
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.PP
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If \fCcpuset\fP overlaps with some existing kinds, those might get modified or split\&. For instance if existing kind A contains PUs 0 and 1, and one registers another kind for PU 1 and 2, there will be 3 resulting kinds: existing kind A is restricted to only PU 0; new kind B contains only PU 1 and combines information from A and from the newly-registered kind; new kind C contains only PU 2 and only gets information from the newly-registered kind\&.
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.PP
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\fBNote\fP
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.RS 4
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The efficiency \fCforced_efficiency\fP provided to this function may be different from the one reported later by \fBhwloc_cpukinds_get_info()\fP because hwloc will scale efficiency values down to between 0 and the number of kinds minus 1\&.
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.RE
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.PP
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\fBReturns\fP
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.RS 4
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\fC0\fP on success\&.
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.PP
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\fC-1\fP with \fCerrno\fP set to \fCEINVAL\fP if some parameters are invalid, for instance if \fCcpuset\fP is \fCNULL\fP or empty\&.
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.RE
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.PP
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.SH "Author"
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.PP
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Generated automatically by Doxygen for Hardware Locality (hwloc) from the source code\&.
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