1 files changed, 76 insertions, 0 deletions
diff --git a/lib/peek/views/memory.rb b/lib/peek/views/memory.rb
new file mode 100644
index 00000000000..399474dedf1
--- /dev/null
+++ b/lib/peek/views/memory.rb
@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module Peek
+  module Views
+    class Memory < View
+      MEM_TOTAL_LABEL = 'Total'
+      MEM_OBJECTS_LABEL = 'Objects allocated'
+      MEM_MALLOCS_LABEL = 'Allocator calls'
+      MEM_BYTES_LABEL = 'Large allocations'
+
+      def initialize(options = {})
+        super
+
+        @thread_memory = {}
+      end
+
+      def results
+        return thread_memory if thread_memory.empty?
+
+        {
+          calls: byte_string(thread_memory[:mem_total_bytes]),
+          summary: {
+            MEM_OBJECTS_LABEL => number_string(thread_memory[:mem_objects]),
+            MEM_MALLOCS_LABEL => number_string(thread_memory[:mem_mallocs]),
+            MEM_BYTES_LABEL => byte_string(thread_memory[:mem_bytes])
+          },
+          details: [
+            {
+              item_header: MEM_TOTAL_LABEL,
+              item_content: "Total memory use of this request. This includes both occupancy of existing heap slots " \
+                            "as well as newly allocated memory due to large objects. Not adjusted for freed memory. " \
+                            "Lower is better."
+            },
+            {
+              item_header: MEM_OBJECTS_LABEL,
+              item_content: "Total number of objects allocated by the Ruby VM during this request. " \
+                            "Not adjusted for objects that were freed again. Lower is better."
+            },
+            {
+              item_header: MEM_MALLOCS_LABEL,
+              item_content: "Total number of times Ruby had to call `malloc`, the C memory allocator. " \
+                            "This is necessary for objects that are too large to fit into a 40 Byte slot in Ruby's managed heap. " \
+                            "Lower is better."
+            },
+            {
+              item_header: MEM_BYTES_LABEL,
+              item_content: "Memory allocated for objects that did not fit into a heap slot. " \
+                            "Not adjusted for memory that was freed again. Lower is better."
+            }
+          ]
+        }
+      end
+
+      private
+
+      attr_reader :thread_memory
+
+      def setup_subscribers
+        subscribe 'process_action.action_controller' do
+          # Ensure that Peek will see memory instrumentation in `results` by triggering it when
+          # a request is done processing. Peek itself hooks into the same notification:
+          # https://github.com/peek/peek/blob/master/lib/peek/railtie.rb
+          Gitlab::InstrumentationHelper.instrument_thread_memory_allocations(thread_memory)
+        end
+      end
+
+      def byte_string(bytes)
+        ActiveSupport::NumberHelper.number_to_human_size(bytes)
+      end
+
+      def number_string(num)
+        ActiveSupport::NumberHelper.number_to_human(num, units: { thousand: 'k', million: 'M', billion: 'B' })
+      end
+    end
+  end
+end