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Tracy-based expr evaluation profiler #9967

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Tracy-based expr evaluation profiler #9967

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Commits on Feb 8, 2024

  1. Naive build system setup 

    This is a first quick-and-dirty way to get the tracy integration up
and running without losing my sanity trying to bend the autotools
setup to work with it.

Introducing a tracy submodule, injecting the required headers from
here, building the TracyClient.cpp file to get the actual tracy client
library.
    @picnoir
    picnoir committed Feb 8, 2024
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  2. Trace the eval.cc functions with Tracy 

    We're leveraging the ZoneTransientN macro to send dynamic strings
containing the expression type, file and position in that file of the
expression Nix is currently evaluating.

We had to add a new showExprType method to the Expr class to get a
const string containing the name of an expression.
    @picnoir
    picnoir committed Feb 8, 2024
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  3. Tracing EvalState members 

    Two expressions evaluations seem to be contained in the EvalState
class. Tracing them as well through a new macro.
    @picnoir
    picnoir committed Feb 8, 2024
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  4. Tracing primops 

    Tracing the primops with Tracy as well. Not sure it really worth the
overhead, but we still can revisit this decision later if we realize
primops are not that important perf-wise.
    @picnoir
    picnoir committed Feb 8, 2024
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  5. Tracy: autotools setup 

    Well, this was as painful as expected.

Introducing a proper autotool-based tracy build. I don't think this is
the right approach, but hey, it works.

Tracy is not distributing any pkg-config file, so we had to fallback
to a more "manual" method to propagate the headers path. Instead of
having a plain enable/disable flag, we send the path to the tracy
/public subfolder (~= $out in the Tracy Nix derivation).

The flake Nixpkgs is currently pointing to 23.05. The tracy derivation
was only building the visualizer, not the client library back then. We
introduce a 23.11 Nixpkgs and build its Tracy derivation with the
23.05 toolchain to go around some glibc ABI incompatibilities.

Kudos to Mic92 for the help for the flake bit.

Co-authored-by: Jörg Thalheim <[email protected]>
    @picnoir @Mic92
    picnoir and Mic92 committed Feb 8, 2024
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