Using CTPIO with Onload

Onload User Guide (UG1586)

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1.2 English

On the X2 series adapter, CTPIO is enabled by default in sf-np mode. The following Onload environment variables are used to configure CTPIO:

Table 1. Environment Variables for Configuring CTPIO
EF Variable Settings

0 disable

1 enable (default)

2 enable, fail if not available


ct cut-through mode (not supported for 25 Gb)

sf store-and-forward mode

sf-np store-and-forward-no-poison (default)


Integer value

Packets with length exceeding this value are not sent via CTPIO, but are sent using the legacy DMA datapath.

Latency-best Profile

Onload-201805 includes a new low latency profile that enables CTPIO in cut-through mode to deliver lowest CTPIO latency:

# onload --profile=latency-best <application, args>

Before using this profile, please read The latency-best Profile, especially the warning on usage.