[PATCH] D133083: [support] Allow TimeProfiler tracing across threads

[Mark Shields via Phabricator via llvm-commits]

mbs-modular updated this revision to Diff 461976.
mbs-modular added a comment.

[support] Allow TimeProfiler tracing across threads

This change allows a TimeProfiler profiling entry to be created on one thread and finished on another. This
was triggered by a use case where we needed to trace the scheduling delay for work items ultimately handled by
independent worker threads.  The clock is changed to std::chrono::high_resolution_clock, both for its
increased precision (our work items can be in the us range), but also for its cross-thread consistency (all
threads see the same clock).

As a pleasant side effect it is now possible to pay for the cost of constructing a profiling entry with a
possibly expensive detail string outside of the critical section we wish to trace. I think we could do better
with shifting the cost of constructing detail strings to the final trace writing phase, given the API already
supports providing detail strings via a callback. But I've not audited the code to check if detail closures
could have their lifetimes safely extended so dramatically.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133083/new/

https://reviews.llvm.org/D133083

Files:
  llvm/include/llvm/Support/TimeProfiler.h
  llvm/lib/Support/TimeProfiler.cpp
  llvm/unittests/Support/TimeProfilerTest.cpp

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