Hi Stefan, I've been starting to use qemu tracing and found it quite
useful. I have a couple comments about the trace events in general:
The event timestamps are host time (get_clock()). I'm correlating qemu
events with other logs (using icount), so host time is unhelpful. Could
we use cpu_get_clock() instead? (Trace events are used in other tools
like qemu-io, where guest time doesn't exist, and there we could
continue to use get_clock().)
When trying to understand multi-core guest behavior, it's pretty
important to know which core is performing the traced action (e.g.
MMIO). Would it make sense to automatically embed the core index, like
the timestamp, or do you think it should be encoded in each individual
tracepoint?
Right now, the simple tracepoint backend creates a trace file even when
no events are active and no -trace options are present. Compounding the
situation, omitting "-trace file=foo" results in the directory being
littered with trace-NNNN files... could we create the file only when
tracing is activated? And maybe with a more predictable name?
--
Hollis Blanchard
Mentor Graphics Emulation Division
