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We (Julia) ship both support for using tracy to trace julia applications, as well as using `rr` (https://github.com/rr-debugger/rr) for record-replay debugging. After our most recent rebuild of tracy, users have been reporting signfificant performance slowdowns when `rr` recording a session that happens to also load the tracy library (even if tracing is not enabled). Upon further examination, the recompile happened to trigger a protective heuristic that disabled rr's patching of tracy's use of `rdtsc` because an earlier part of the same function happened to look like a conditional branch into the patch region. See https://github.com/rr-debugger/rr/pull/3580 for details. To avoid this issue occurring again in future rebuilds of tracy, adjust tracy's `rdtsc` sequence to be `nopl; rdtsc`, which (as of of the linked PR) is a sequence that is guaranteed to bypass this heuristic and not incur the additional overhead when run under rr. This functionality is kept behind a compile-time flag `TRACY_PATCHABLE_NOPSLEDS` in order to avoid polluting the instruction cache unnecessarily. |
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| .. | ||
| client | ||
| common | ||
| libbacktrace | ||
| tracy | ||
| TracyClient.cpp | ||