trace: when profiling, dump a sampling trace #671
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Whenever we run under the profiling flag, we now collect sampling traces into .urb/put/trace/dump.txt. We take care to format the output in a way that's compatible with flamegraph tooling. Specifically, we avoid writing into the first couple lines of the file, and suffix every trace with a counter (always 1). (See also brendangregg/FlameGraph.) We have not yet cleaned up old code in u3t_samp. Co-authored-by: joemfb <joemfb@gmail.com>
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Whenever we run under the profiling flag (
-P--profile), we now collect sampling traces into.urb/put/trace/dump.txt.We take care to format the output in a way that's compatible with flamegraph tooling. Specifically, we avoid writing into the first couple lines of the file, and suffix every trace with a counter (always 1), to mimic dtrace output.
(See also brendangregg/FlameGraph.)
We have not yet cleaned up old code in
u3t_samp.After running some ship with
--profile, we can use the flamegraph scripts to turn the dump into an svg:If the ship ran
-build-file %/sys/hoon/hoonunder the profiler, the resulting svg might look something like this: