User`s guide

Chapter 4
Performance Tuning
The default settings have been carefully chosen to maximize throughput for the SGI
10-Gigabit (Gbit) Ethernet PCI Express network adapter so that no further tuning is
required. However, if you wish to experiment with the settings found on Myricom’s
web site at http://www.myri.com/serve/cache/511.html, it is important that you
follow the information in this chapter.
This chapter discusses the following:
• "Jumbo Frames" on page 13
• "Read/Write Size" on page 13
• "Network Buffer Sizes" on page 13
• "TCP Time Stamps" on page 14
Jumbo Frames
Using a large maximum transmission unit (MTU) is necessary for the best 10–Gbit
Ethernet performance. Generally, the bigger the MTU, the better. The driver supports
MTUs as large as 9000 bytes.
Read/Write Size
Applications should read large buffers from and write large buffers to the network for
the best throughput and to reduce CPU utilization.
For example, an application that uses recv(2) calls with 32–KB buffers will generally
have better throughput than if the application were to use twice as many recv calls
with 16-KB buffers.
Network Buffer Sizes
Normally, larger network buffers are called for with 10-Gbit Ethernet than when
lower-bandwidth network interface cards are used. The following network buffer
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