Oct 15 – 16, 2016
The Fairmont Dallas
US/Central timezone

Nameserver UDP socket buffer tuning

Oct 16, 2016, 4:15 PM
Gold (The Fairmont Dallas)


The Fairmont Dallas

1717 N Akard St Dallas, TX 75201 USA
Standard Presentation Public Workshop Public Workshop


Mr Ciprian Dan Cosma (Amazon)


**Background:** The size of the UDP buffers has a significant impact on nameserver performance and, as such, is a decision that has to be taken for all DNS deployments. Due to the interaction between operating system memory allocation strategies, TCP/IP stack implementation, buffer accounting, and application software there are a lot of misunderstandings about what is the appropriate value and what are the overheads involved. By using a combination of tests, kernel source inspection, and Systemtap scripts, we aim to clarify how buffer accounting works and what is the correct process for calculating the necessary buffers. **Results:** Socket buffers are slab allocated, so they present a non-linear overhead characteristic. This leads to overhead of up to 2000% for common DNS packet sizes. Buffer size vs packet size are investigated for IPv4 and IPv6 for payload sizes between 1byte and 4kB. Using Systemtap, we analyze buffer contents and data structure sizes in different Linux kernels.
Talk duration 30 Minutes

Primary author

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