Add a Gitlab::Profiler.print_by_total_time convenience method

This method uses Gitlab::Profiler::TotalTimeFlatPrinter internally, which is the
same as RubyProf::FlatPrinter, but the min_percent option (and new max_percent
option) applies to the _total_ time, not the _self_ time. This helps us figure
out if we're calling a library inefficiently, for instance.

1 files changed, 39 insertions, 0 deletions

diff --git a/lib/gitlab/profiler/total_time_flat_printer.rb b/lib/gitlab/profiler/total_time_flat_printer.rb
new file mode 100644
index 00000000000..2fd0ec10ba8
--- /dev/null
+++ b/lib/gitlab/profiler/total_time_flat_printer.rb
@@ -0,0 +1,39 @@
+module Gitlab
+  module Profiler
+    class TotalTimeFlatPrinter < RubyProf::FlatPrinter
+      def max_percent
+        @options[:max_percent] || 100
+      end
+
+      # Copied from:
+      #   <https://github.com/ruby-prof/ruby-prof/blob/master/lib/ruby-prof/printers/flat_printer.rb>
+      #
+      # The changes are just to filter by total time, not self time, and add a
+      # max_percent option as well.
+      def print_methods(thread)
+        total_time = thread.total_time
+        methods = thread.methods.sort_by(&sort_method).reverse
+
+        sum = 0
+        methods.each do |method|
+          total_percent = (method.total_time / total_time) * 100
+          next if total_percent < min_percent
+          next if total_percent > max_percent
+
+          sum += method.self_time
+
+          @output << "%6.2f  %9.3f %9.3f %9.3f %9.3f %8d  %s%s\n" % [
+            method.self_time / total_time * 100, # %self
+            method.total_time,                   # total
+            method.self_time,                    # self
+            method.wait_time,                    # wait
+            method.children_time,                # children
+            method.called,                       # calls
+            method.recursive? ? "*" : " ",       # cycle
+            method_name(method)                  # name
+          ]
+        end
+      end
+    end
+  end
+end