Chelsio Communications Chelsio T4, Инструкция по установке и эксплуатации

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Chapter VI. WD-UDP
Chelsio T5/T4 Unified Wire for Linux
Page 93
4. Software/Driver Configuration and Fine-tuning
4.1. Accelerating UDP Socket communications
The libcxgb4_sock library is a LD_PRELOAD-able library that accelerates UDP Socket
communications transparently and without recompilation of the user application. This section
describes how to use libcxgb4_sock.
By preloading libcxgb4_sock , all sockets created by the application are intercepted and possibly
accelerated based on the user’s configuration. Once accelerated, data for the UDP endpoint are
transmitted or received via HW queues allocated specifically for the accelerated endpoint,
bypassing the kernel, the host networking stack and sockets framework, and enabling ultra-low
latency and high bandwidth utilization.
Due to HW resource limitations, only a small number of queues can be allocated for UDP
acceleration. Therefore only performance critical UDP applications should use
libcxgb4_sock .
Only 64 IPv4 UDP / 28 IPv6 UDP sockets can be accelerated per Chelsio T5/T4 device,
with
Unified Wire Configuration tuning option. If you want more sockets to be
accelerated, please use Low Latency or High Capacity WD tuning option.
4.1.1. Application Requirements
Certain application behavior is not supported by libcxb4_sock in this release. If your application
does any of the following, it will not work with libcxgb4_sock :
Calling fork() after creating UDP sockets and using the UDP socket in the child process.
Using multiple threads on a single UDP socket without serialization. For instance, having
one thread sending concurrently with another thread receiving. If your application does this,
you need to serialize these paths with a spin or mutex lock.
Only 1 UDP endpoint is allowed to bind to a given port per host. So if you have multiple
processes on the same host binding to the same UDP port number, you cannot use
libcxgb4_sock .
Applications must have root privileges to use libcxgb4_sock .
Applications requiring bonded T5/T4 interfaces are not currently supported.
The performance benefit observed with libcxgb4_sock
will vary based on your application’s
behavior. While all UDP IO is handled properly, only certain datagrams are accelerated. Non
accelerated IO is handled by
libcxgb4_sock via the host networking stack seamlessly. Both
Unicast and Multicast datagrams can be accelerated, but the datagrams must meet the
following criteria:
Non fragmented. In other words, they fit in a single IP datagram that is <= the T5/T4 device
MTU.