feat(tools): Add script to flamegraph a command

Add tools.perf-flamegraph, which collects the base case execution of
perf piped through stackcollapse-perf and flamegraph to flamegraph the
execution of an external command via perf.

Change-Id: I671fe254dc374b6cd7deca2d3bdea266164de025
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1176
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

bin/__dispatch.sh

@@ -40,6 +40,9 @@ case "${TARGET_TOOL}" in
   ninja)
     attr="third_party.ninja"
     ;;
+  perf-flamegraph)
+    attr="tools.perf-flamegraph"
+    ;;
   rebuild-system)
     attr="ops.nixos.rebuild-system"
     ;;

bin/perf-flamegraph

@@ -0,0 +1 @@
+__dispatch.sh

third_party/default.nix

@@ -72,6 +72,7 @@ let
       fira
       fira-code
       fira-mono
+      flamegraph
       fontconfig
       freetype
       gettext
@@ -92,6 +93,7 @@ let
       kontemplate
       lib
       libredirect
+      linuxPackages
       luajit
       lutris
       makeFontsConf

tools/perf-flamegraph.nix

@@ -0,0 +1,12 @@
+# Script that collects perf timing for the execution of a command and writes a
+# flamegraph to stdout
+{ pkgs, ... }:
+
+pkgs.writeShellScriptBin "perf-flamegraph" ''
+  set -euo pipefail
+
+  ${pkgs.linuxPackages.perf}/bin/perf record -g -a -F max "$@"
+  ${pkgs.linuxPackages.perf}/bin/perf script \
+    | ${pkgs.flamegraph}/bin/stackcollapse-perf.pl \
+    | ${pkgs.flamegraph}/bin/flamegraph.pl
+''