glances/docs/aoa/cpu.rst
2017-05-08 09:46:40 +02:00

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.. _cpu:
CPU
===
The CPU stats are shown as a percentage or values and for the configured
refresh time.
The total CPU usage is displayed on the first line.
.. image:: ../_static/cpu.png
If enough horizontal space is available, extended CPU information are
displayed.
.. image:: ../_static/cpu-wide.png
A character is also displayed just after the CPU header and shows the
trend value:
======== ==============================================================
Trend Status
======== ==============================================================
``-`` CPU value is equal to the mean of the six latests refreshes
``\`` CPU value is lower than the mean of the six latests refreshes
``/`` CPU value is higher than the mean of the six latests refreshes
======== ==============================================================
CPU stats description:
- **user**: percent time spent in user space. User CPU time is the time
spent on the processor running your program's code (or code in
libraries).
- **system**: percent time spent in kernel space. System CPU time is the
time spent running code in the Operating System kernel.
- **idle**: percent of CPU used by any program. Every program or task
that runs on a computer system occupies a certain amount of processing
time on the CPU. If the CPU has completed all tasks it is idle.
- **nice** *(\*nix)*: percent time occupied by user level processes with
a positive nice value. The time the CPU has spent running users'
processes that have been *niced*.
- **irq** *(Linux, \*BSD)*: percent time spent servicing/handling
hardware/software interrupts. Time servicing interrupts (hardware +
software).
- **iowait** *(Linux)*: percent time spent by the CPU waiting for I/O
operations to complete.
- **steal** *(Linux)*: percentage of time a virtual CPU waits for a real
CPU while the hypervisor is servicing another virtual processor.
- **ctx_sw**: number of context switches (voluntary + involuntary) per
second. A context switch is a procedure that a computer's CPU (central
processing unit) follows to change from one task (or process) to
another while ensuring that the tasks do not conflict.
- **inter**: number of interrupts per second.
- **sw_inter**: number of software interrupts per second. Always set to
0 on Windows and SunOS.
- **syscal**: number of system calls per second. Do not displayed on
Linux (always 0).
To switch to per-CPU stats, just hit the ``1`` key:
.. image:: ../_static/per-cpu.png
By default, ``steal`` CPU time alerts aren't logged. If you want that,
just add to the configuration file:
.. code-block:: ini
[cpu]
steal_log=True
Legend:
================= ============
CPU (user/system) Status
================= ============
``<50%`` ``OK``
``>50%`` ``CAREFUL``
``>70%`` ``WARNING``
``>90%`` ``CRITICAL``
================= ============
.. note::
Limit values can be overwritten in the configuration file under
the ``[cpu]`` and/or ``[percpu]`` sections.