Chapter 25. Reducing TCP performance spikes

Generating TCP timestamps can result in TCP performance spikes. The sysctl command controls the values of TCP related entries, setting the timestamps kernel parameter found at /proc/sys/net/ipv4/tcp_timestamps.

Prerequisites

  • You have administrator privileges.

25.1. Turning off TCP timestamps

Turning off TCP timestamps can reduce TCP performance spikes.

Procedure

  • Turn off TCP timestamps: 

    # sysctl -w net.ipv4.tcp_timestamps=0
net.ipv4.tcp_timestamps = 0

    The output shows that the value of net.ip4.tcp_timestamps options is 0. That is, TCP timestamps are disabled.

25.2. Turning on TCP timestamps

Generating timestamps can cause TCP performance spikes. You can reduce TCP performance spikes by disabling TCP timestamps. If you find that generating TCP timestamps is not causing TCP performance spikes, you can enable them.

Procedure

  • Enable TCP timestamps. 

    # sysctl -w net.ipv4.tcp_timestamps=1
net.ipv4.tcp_timestamps = 1

    The output shows that the value of net.ip4.tcp_timestamps is 1. That is, TCP timestamps are enabled.

25.3. Displaying the TCP timestamp status

You can view the status of TCP timestamp generation.

Procedure

  • Display the TCP timestamp generation status: 

    # sysctl net.ipv4.tcp_timestamps
net.ipv4.tcp_timestamps = 0

    The value 1 indicates that timestamps are being generated. The value 0 indicates timestamps are being not generated.