Precision Time Protocol (Ptp) - Chelsio Communications Terminator Series Installation And User Manual

Chapter II. Network (NIC/TOE)
the ability for the socket layer code to poll directly on an Ethernet device's Rx queue. This
eliminates the cost of interrupts and context switching, and with proper tuning allows to achieve
latency performance similar to that of hardware.
Chelsio's NIC and TOE drivers support this feature and can be enabled on Chelsio supported
devices to attain improved latency.
To make use of BUSY_POLL feature, follow the steps mentioned below:
i. Enable BUSY_POLL support in kernel config file by setting
ii. Enable BUSY_POLL globally in the system by setting the values of following sysctl
parameters depending on the number of connections:
sysctl -w net.core.busy_read=<value>
sysctl -w net.core.busy_poll=<value>
Set the values of the above parameters to 50 for 100 or less connections; and 100 for more
than 100 connections.
BUSY_POLL can also be enabled on a per-connection basis by making use of
Note
SO_BUSY_POLL option in the socket application code. Refer socket man-page for
more details.
4.3.

Precision Time Protocol (PTP)

Precision Time Protocol (PTP) standard defines a protocol for precise synchronization of clock
between master and slave devices in a local area network. It can provide timing accuracies in
nanosecond units. The protocol is based on time stamping and measuring the send and receive
times. Most of the implementation relies on time stamping of the packets in the software which
reduces the accuracy of the time measured. One possible solution to this problem is time
stamping the packet in the NIC hardware itself.
Chelsio's Terminator hardware provides many features to support PTP implementations:
•
High precision timers which can be read through PIO registers.
•
Wall clock time based on the time of the day.
•
Time stamping of selected PTP packets on both ingress and egress direction.
This feature is currently supported on RHEL 7.5, RHEL 7.4, SLES 12 SP3 and
Important
kernels 4.14 and 4.9.105.
Synchronizing Clocks
ptp4l tool (installed during Unified Wire installation) is used to synchronise clocks:
Chelsio Unified Wire for Linux
CONFIG_NET_RX_BUSY_POLL=y
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