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Track function start and ends for flame graphs

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With this patch, and this file I called `log.py`:

    #!/usr/bin/env nix-shell
    #!nix-shell -i python3 -p python3 --pure

    import sys
    from pprint import pprint

    stack = []
    timestack = []

    for line in open(sys.argv[1]):
        components = line.strip().split(" ", 2)
        if components[0] != "function-trace":
            continue

        direction = components[1]
        components = components[2].rsplit(" ", 2)

        loc = components[0]
        _at = components[1]
        time = int(components[2])

        if direction == "entered":
            stack.append(loc)
            timestack.append(time)
        elif direction == "exited":
            dur = time - timestack.pop()
            vst = ";".join(stack)
            print(f"{vst} {dur}")
            stack.pop()

and:

    nix-instantiate --trace-function-calls -vvvv ../nixpkgs/pkgs/top-level/release.nix -A unstable > log.matthewbauer 2>&1
    ./log.py ./log.matthewbauer > log.matthewbauer.folded
    flamegraph.pl --title matthewbauer-post-pr log.matthewbauer.folded > log.matthewbauer.folded.svg

I can make flame graphs like: http://gsc.io/log.matthewbauer.folded.svg

---

Includes test cases around function call failures and tryEval. Uses
RAII so the finish is always called at the end of the function.
This commit is contained in:
Graham Christensen 2019-04-12 12:31:33 -04:00
parent 1eeaf99cf8
commit ee9c988a1b
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GPG key ID: ACA1C1D120C83D5C
7 changed files with 189 additions and 3 deletions
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4
src/libexpr/eval.hh
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@ -6,6 +6,7 @@
#include "symbol-table.hh"
#include "hash.hh"
#include "config.hh"
#include "function-trace.hh"
#include <map>
#include <unordered_map>
@ -349,6 +350,9 @@ struct EvalSettings : Config
Setting<Strings> allowedUris{this, {}, "allowed-uris",
"Prefixes of URIs that builtin functions such as fetchurl and fetchGit are allowed to fetch."};
Setting<bool> traceFunctionCalls{this, false, "trace-function-calls",
"Emit log messages for each function entry and exit at the 'vomit' log level (-vvvv)"};
};
extern EvalSettings evalSettings;