Tracing

This document describes the way for debugging and profiling in StratoVirt and how to use it.

Ftrace

Ftrace is a tracer provided by Linux kernel, which can help linux developers to debug or analyze issues. As ftrace can avoid performance penalty, it's especially suited for performance issues.

StratoVirt use ftrace by writing trace data to ftrace marker, and developers can read trace records from trace file under mounted ftrace director, e.g. /sys/kernel/debug/tracing/trace.

How to use

Trace events are put in StratoVirt by the macro ftrace!. The first parameter the macro receives is name of the trace event. Remaining parameters the macro receives are the same as println! or format!, i.e. the first parameter is a format string, and additional parameters passed replace the {}s within the format string.

#[macro_use]
extern crate util;

fn trace_example() {
    ftrace!(trace_example, "Test for tracer.");
}

Trace events in StratoVirt are disabled by default. Users can pass the file listing enabled events by launching StratoVirt with "-trace events=". The file should contains one event name per line.