Xilinx Alveo X3522 User Manual page 38

The above examples set both the receive and the transmit interrupt moderation interval. Packet
RX and TX completions share interrupts, so RX and TX interrupt moderation intervals must be
equal, and the adapter driver automatically adjusts tx-usecs to match rx-usecs.
Interrupt moderation settings can be checked using ethtool –c .
TCP/IP Checksum Offload
Checksum offload moves calculation and verification of IP Header, TCP and UDP packet
checksums to the adapter. The driver has all checksum offload features enabled by default.
Therefore, there is no opportunity to improve performance from the default.
Receive checksum offload is controlled using ethtool:
# /sbin/ethtool –K <interface> rx <on|off>
As it is fully cut-through, the X3522 does not support TCP/IP checksum offload on transmit.
Verification of the checksum settings can be performed by running ethtool with the –k option.
Note: It is not recommended to disable the checksum offload.
TCP Protocol Tuning
TCP performance can also be improved by tuning kernel TCP settings. Settings include adjusting
send and receive buffer sizes, connection backlog, congestion control, etc.
Initial buffering settings should provide good performance. However, for certain applications,
tuning buffer settings can significantly benefit throughput. To change buffer settings, adjust the
tcp_rmem and tcp_wmem using the sysctl command:
• Receive buffering:
sysctl net.ipv4.tcp_rmem="<min> <default> <max>"
• Transmit buffering:
sysctl net.ipv4.tcp_wmem="<min> <default> <max>"
(tcp_rmem and tcp_wmem can also be adjusted for IPV6 and globally with the net.ipv6 and
net.core variable prefixes respectively).
Typically it is sufficient to tune just the max buffer value. It defines the largest size the buffer can
grow to. Suggested alternate values are max=500000 (1/2 Mbyte). Factors such as link latency,
packet loss, and CPU cache size all influence the affect of the max buffer size values. The
minimum and default values can be left at their defaults minimum=4096 and default=87380.
UG1523 (v1.0) October 18, 2022
Alveo X3522 User Guide
Chapter 5: Tuning
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