ssllatency.bt - Man Page

ssllatency.bt

ssllatency shows latency distribution for OpenSSL handshake functions. This is useful for performance analysis with different crypto cipher suite, async SSL acceleration by CPU or offload device, etc.

This tool works by dynamic tracing the uprobes in OpenSSL and related crypto libs, and may need updating to match future changes to these functions.

Since this uses BPF, only the root user can use this tool.

CONFIG_BPF and bpftrace.

Trace SSL/TLS handshake latency, and print a histogram on Ctrl-C:

# ssllatency.bt

0th

A function name is shown in "@hist[...]" followed by latency histogram and "@stat[...]" followed by total call count, average, total latency in microseconds. Non-zero failed calls are traced separately (in "@histF[]" and "@statF[]") for some functions.

1st, 2nd

This is a range of latency, in microseconds (shown in "[...)" set notation).

3rd

A column showing the count of operations in this range.

4th

This is an ASCII histogram representing the count column.

SSL/TLS handshake usually contains network latency and the traced crypto functions are CPU intensive tasks, so call frequency should be low and the overhead of this tool is expected to be negligible.

This is from bpftrace.

https://github.com/iovisor/bpftrace

Also look in the bpftrace distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.

There is a bcc tool sslsniff that can show SSL/TLS handshake event latency before sniffing the plaintext in SSL_read/write. This tool provides more detailed crypto latency distribution during the handshake event.

https://github.com/iovisor/bcc

Linux

Unstable - in development.

Tao Xu

sslsnoop.bt(8)