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.. _mongoperf:
.. default-domain:: mongodb
:program:`mongoperf` is a utility to check disk I/O performance
independently of MongoDB.
It times tests of random disk I/O and presents the results. You can
use :program:`mongoperf` for any case apart from MongoDB. The
:setting:`~mongoperf.mmf` ``true`` mode is completely generic. In
that mode it is somewhat analogous to tools such as `bonnie++
<>`_ (albeit mongoperf is
Specify options to :program:`mongoperf` using a JavaScript document.
.. seealso::
* `bonnie <>`_
* `bonnie++ <>`_
* `Output from an example run <>`_
* `Checking Disk Performance with the mongoperf Utility <>`_
.. _mongoperf-options:
.. binary:: mongoperf
.. program:: mongoperf
.. option:: --help
Displays the options to :program:`mongoperf`. Specify options to
:program:`mongoperf` with a JSON document described in the
:ref:`mongoperf-fields` section.
.. option:: <jsonconfig>
:program:`mongoperf` accepts configuration options in the form of a
file that holds a :term:`JSON` document. You must stream the
content of this file into :program:`mongoperf`, as in the following
.. code-block:: sh
mongoperf < config
In this example ``config`` is the name of a file that holds a JSON
document that resembles the following example:
.. code-block:: javascript
See the :ref:`mongoperf-fields` section for documentation of each
of these fields.
.. _mongoperf-fields:
Configuration Fields
.. setting:: mongoperf.nThreads
*Type:* Integer.
*Default:* 1
Defines the number of threads :program:`mongoperf` will use in the
test. To saturate your system's storage system you will need
multiple threads. Consider setting :setting:`~mongoperf.nThreads` to ``16``.
.. setting:: mongoperf.fileSizeMB
*Type:* Integer.
*Default:* 1 megabyte (i.e. 1024\ :sup:`2` bytes)
Test file size.
.. setting:: mongoperf.sleepMicros
*Type:* Integer.
*Default:* 0
:program:`mongoperf` will pause for the number of specified
:setting:`~mongoperf.sleepMicros` divided by the
:setting:`~mongoperf.nThreads` between each operation.
.. setting:: mongoperf.mmf
*Type:* Boolean.
*Default:* ``false``
Set :setting:`~mongoperf.mmf` to ``true`` to use memory mapped
files for the tests.
- when :setting:`~mongoperf.mmf` is ``false``, :program:`mongoperf`
tests direct, physical, I/O, without caching. Use a large file
size to test heavy random I/O load and to avoid I/O coalescing.
- when :setting:`~mongoperf.mmf` is ``true``, :program:`mongoperf`
runs tests of the caching system, and can use normal file system
cache. Use :setting:`~mongoperf.mmf` in this mode to test file system cache
behavior with memory mapped files.
.. setting:: mongoperf.r
*Type:* Boolean.
*Default:* ``false``
Set :setting:`~mongoperf.r` to ``true`` to perform reads as part of
the tests.
Either :setting:`~mongoperf.r` or :setting:`~mongoperf.w` must be ``true``.
.. setting:: mongoperf.w
*Type:* Boolean.
*Default:* ``false``
Set :setting:`~mongoperf.w` to ``true`` to perform writes as part of
the tests.
Either :setting:`~mongoperf.r` or :setting:`~mongoperf.w` must be ``true``.
.. setting:: mongoperf.recSizeKB
.. versionadded:: 2.4
*Type:* Integer.
*Default:* 4 kb
The size of each write operation.
.. setting:: mongoperf.syncDelay
*Type:* Integer.
*Default:* 0
Seconds between disk flushes. :setting:`mongoperf.syncDelay` is
similar to :option:`--syncdelay <mongod --syncdelay>` for :program:`mongod`.
The :setting:`~mongoperf.syncDelay` controls how frequently
:program:`mongoperf` performs an asynchronous disk flush of the memory
mapped file used for testing. By default, :program:`mongod`
performs this operation every 60 seconds. Use
:setting:`~mongoperf.syncDelay` to test basic system performance of
this type of operation.
Only use :setting:`~mongoperf.syncDelay` in conjunction with
:setting:`~mongoperf.mmf` set to ``true``.
The default value of ``0`` disables this.
.. code-block:: javascript
mongoperf < jsonconfigfile
Replace ``jsonconfigfile`` with the path to the :program:`mongoperf`
configuration. You may also invoke :program:`mongoperf` in the
following form:
.. code-block:: sh
echo "{nThreads:16,fileSizeMB:1000,r:true}" | ./mongoperf
In this operation:
- :program:`mongoperf` tests direct physical random read io's, using
16 concurrent reader threads.
- :program:`mongoperf` uses a 1 gigabyte test file.
Consider using ``iostat``, as invoked in the following example to
monitor I/O performance during the test.
.. code-block:: sh
iostat -xm 2
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