lix/src/libexpr/function-trace.hh
Graham Christensen ee9c988a1b
Track function start and ends for flame graphs
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.
2019-08-14 16:09:35 -04:00

25 lines
692 B
C++

#pragma once
#include "eval.hh"
#include <sys/time.h>
namespace nix {
struct FunctionCallTrace
{
const Pos & pos;
FunctionCallTrace(const Pos & pos) : pos(pos) {
auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
vomit("function-trace entered %1% at %2%", pos, ns.count());
}
~FunctionCallTrace() {
auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
vomit("function-trace exited %1% at %2%", pos, ns.count());
}
};
}