Hi Stefan, just had a closer look at qemu's new tracing framework. Looks cool, though it leaves a bit room for improvements. ;)
One quirk I stumbled over quickly was the "disable" tag in trace-events. It confused me first as qemu starts without any tracepoint enabled by default and I thought I had to hack the file. Then I read the doc and wondered which exiting or future backend would come without sufficiently fast dynamic tracepoint control. Do you have any in mind? Instead of making it a compile-time switch (except for simpletrace), I would vote for declaring the simpletrace usage as the only one: disable sets the default state of the dynamic tracepoint. That way we could use trace-events to define a useful set of standard, moderate-impact tracepoints that shall be on. Others will still be available once a backend is configured, but remain off until enabled during runtime. Anything else looks like overkill to me. There are a few more things I have in mind (ftrace backend, enhanced "-trace" switch, wildcards for enabling tracepoints, and more tracepoints). Will hopefully come up with patches to address them, but this may take a while. Jan PS: Do you maintain a tracing git tree? -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
