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# 3 Discovery of CPUs and CPU cores

In a similar way as [file
systems](/manual/discovery/low_level_discovery#configuring_low-level_discovery)
are discovered, it is possible to also discover CPUs and CPU cores.

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#### Item key

The item key to use in the [discovery
rule](/manual/discovery/low_level_discovery#discovery_rule) is

    system.cpu.discovery

This item is supported since Zabbix agent 2.4.

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#### Supported macros

This discovery key returns two macros - {\#CPU.NUMBER} and
{\#CPU.STATUS} identifying the CPU order number and status respectively.
Note that a clear distinction cannot be made between actual, physical
processors, cores and hyperthreads. {\#CPU.STATUS} on Linux, UNIX and
BSD systems returns the status of the processor, which can be either
"online" or "offline". On Windows systems, this same macro may represent
a third value - "unknown" - which indicates that a processor has been
detected, but no information has been collected for it yet.

CPU discovery relies on the agent's collector process to remain
consistent with the data provided by the collector and save resources on
obtaining the data. This has the effect of this item key not working
with the test (-t) command line flag of the agent binary, which will
return a NOT\_SUPPORTED status and an accompanying message indicating
that the collector process has not been started.

Item prototypes that can be created based on CPU discovery include, for
example:

-   `system.cpu.util[{#CPU.NUMBER},<type>,<mode>]`
-   `system.hw.cpu[{#CPU.NUMBER},<info>]`

For detailed item key description, see [Zabbix agent item
keys](/manual/config/items/itemtypes/zabbix_agent#supported_item_keys).

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#### Notes on discovered performance counter items on NUMA systems

Some [Windows performance counters](/manual/config/items/perfcounters) might be not available for some of the logical processors at NUMA systems.

For example, items discovered with an item prototype with the key below might work only for the first NUMA node. Items for the other NUMA nodes might be in unsupported state.

```
perf_counter[\Processor({#CPU.NUMBER})\% Processor Time,60]
```

Also, a discovery rule with key "system.cpu.discovery" does not provide any low-level discovery macro values to substitute into such performance counters as:

```
perf_counter["\Processor Information(<NUMA node index>,<CPU index in NUMA node>)\% Processor Time",60]
```

While [system.cpu.util](/manual/appendix/items/system_cpu_util) items rely on different performance counters
to monitor CPU utilization percentage depending on the processor group count and processor count.
Also, there is a rare bug related to [processor groups on Windows](/manual/installation/known_issues#win-proc-groups).

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