.. index:: pair: group; Setting rx_coalesce_usecs to a specific value
.. _doxid-group__rx__path-rx__coalesce__usecs:

Setting rx_coalesce_usecs to a specific value
=============================================

.. toctree::
	:hidden:

Check that when **rx_coalesce_usecs** is set to a specific value, Rx interrupts coalescing works accordingly.



#. Establish connection between a pair of UDP sockets on IUT and Tester.

#. Send a packet from Tester and receive it on IUT to be sure that IUT IP address is resolved.

#. Disable **use_adaptive_rx_coalesce** on IUT interface.

#. Set **rx_coalesce_usecs** to the value of **coalesce_usecs** for the IUT interface. Also for nonzero **coalesce_usecs** set **rx_max_coalesced_frames** to zero so that it is not taken into account when coalescing; for zero **coalesce_usecs** set it to ``1``.
   
   * If setting fails with ``EOPNOTSUPP``, try to set only **rx_coalesce_usecs**, as setting **rx_max_coalesced_frames** may be not available.

#. Create a CSAP on Tester to capture packets sent from it to IUT.

#. Create a CSAP on IUT to capture packets received from Tester.

#. For some time send UDP packets from Tester to IUT, waiting a little after sending every packet. Receive and check data on IUT.

#. Investigate timestamps of Tx packets captured by Tester CSAP. Memorize numbers of packets sent after big delays to ignore them when computing coalescing statistics on IUT.

#. Investigate timestamps of packets captured by CSAP on IUT. If **coalesce_usecs** is ``0``, there should be only small delays after every packet. If **coalesce_usecs** is not zero, packets should be received in groups separated by larger delays.

Dmitry Izbitsky `Dmitry.Izbitsky@oktetlabs.ru <mailto:Dmitry.Izbitsky@oktetlabs.ru>`__



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- env

		- 
		  Testing environment:
		  
		  * :ref:`env.peer2peer <doxid-group__env-peer2peer>`
		  
		  * :ref:`env.peer2peer_ipv6 <doxid-group__env-peer2peer__ipv6>`

	*
		- coalesce_usecs

		- 
		  Value to set for **rx_coalesce_usecs:**
		  
		  * ``0`` (interrupt moderation is disabled)
		  
		  * ``300``
		  
		  * ``800``