README.sfnt-stream.md

sfnt-stream

Introduction

sfnt-stream measures streaming latency for a fixed message size over a range of message rates. At time of writing it only works with UDP sockets, but will be extended to support other protocols and IPC mechanisms later.

Measuring network latency

To measure latency and message rate over a network, first start a "server" instance on one node:

host1$ sfnt-stream

Then start a "client" instance on another node, passing the name of the server node as follows:

host2$ sfnt-stream udp host1 # for UDP

host2$ sfnt-stream --mcastintf=ethX udp host1 # for UDP multicast

If running sfnt-stream with OpenOnload or EnterpriseOnload, we recommend you enable the option EF_STACK_PER_THREAD=1 at the client side (host2 above) for best performance.

Options

There are numerous options to control details of the test. Options are given on the client's command line -- the server side should be invoked with no arguments. Some options apply only on the client side, and others apply to both client and server. For options that apply to both sides, you can either supply a single value that is used on both the client and server. eg:

    --mcastintf=eth2          # use interface eth2 on client and server

Or you can give two values separated by ;. The first applies to the client, and the second to the server. eg:

    --mcastintf='eth2;eth3'   # use eth2 on client and eth3 on server

Note the quoting needed to prevent the shell from interpreting the ;.

Here is a brief overview of the available options:

• An option to "spin" making non-blocking calls (--spin)
• An option to use select, poll or epoll for blocking (--muxer)
• Options to add more file descriptors to select, poll and epoll (--n-pipe, --n-udp, --n-tcpc, --n-tcpl)
• Options to control multicast (--mcastintf, --mcast, --mcastloop)
• An option to set CPU affinity (--affinity)

To get the full list, invoke:

sfnt-stream --help

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