1 files changed, 69 insertions, 0 deletions
diff --git a/scripts/perf/gc/print_gc_stats.rb b/scripts/perf/gc/print_gc_stats.rb
new file mode 100755
index 00000000000..4aeb2f1ef07
--- /dev/null
+++ b/scripts/perf/gc/print_gc_stats.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+# Promotes survivors from eden to old gen and runs a compaction.
+#
+# aka "Nakayoshi GC"
+#
+# https://github.com/puma/puma/blob/de632261ac45d7dd85230c83f6af6dd720f1cbd9/lib/puma/util.rb#L26-L35
+def nakayoshi_gc
+  4.times { GC.start(full_mark: false) }
+  GC.compact
+end
+
+# GC::Profiler is used elsewhere in the code base, so we provide a way for it
+# to be used exclusively by this script, or otherwise results will be tainted.
+module GC::Profiler
+  class << self
+    attr_accessor :use_exclusive
+
+    %i[enable disable clear].each do |method|
+      alias_method "#{method}_orig", "#{method}"
+
+      define_method(method) do
+        if use_exclusive
+          warn "GC::Profiler: ignoring call to #{method}"
+          return
+        end
+
+        send("#{method}_orig") # rubocop: disable GitlabSecurity/PublicSend
+      end
+    end
+  end
+end
+
+GC::Profiler.enable
+GC::Profiler.use_exclusive = true
+
+require 'benchmark'
+
+RAILS_ROOT = ENV['RAILS_ROOT']
+
+tms = Benchmark.measure do
+  require RAILS_ROOT + 'config/boot'
+  require RAILS_ROOT + 'config/environment'
+end
+
+GC::Profiler.use_exclusive = false
+
+nakayoshi_gc
+
+gc_stats = GC.stat
+warn gc_stats.inspect
+
+gc_total_time = GC::Profiler.total_time
+
+GC::Profiler.report($stderr)
+GC::Profiler.disable
+
+gc_stat_keys = ENV['GC_STAT_KEYS'].to_s.split(',').map(&:to_sym)
+
+values = []
+values << ENV['SETTING_CSV']
+values += gc_stat_keys.map { |k| gc_stats[k] }
+values << ::Gitlab::Metrics::System.memory_usage_rss
+values << gc_total_time
+values << tms.utime + tms.cutime
+values << tms.stime + tms.cstime
+values << tms.real
+
+puts values.join(',')