Merge branch 'performance-clock-adjustments' into 'master'

Use clock_gettime for all performance timestamps

This MR adjusts the performance monitoring code to use `Process.clock_gettime` (thus `clock_gettime(3)`) instead of `Time.now`.

Using `Time.now` / `Time.new` adds more overhead than `Process.clock_gettime`, it also doesn't provide a way of getting timestamps in nanoseconds (which `Process.clock_gettime` does allow).

See merge request !4899
(cherry picked from commit 53ad9522c46edf8ede068145fa3d89e2b047c076)

1 files changed, 14 insertions, 2 deletions

diff --git a/spec/lib/gitlab/metrics/system_spec.rb b/spec/lib/gitlab/metrics/system_spec.rb
index d6ae54e25e8..cf0e282c2fb 100644
--- a/spec/lib/gitlab/metrics/system_spec.rb
+++ b/spec/lib/gitlab/metrics/system_spec.rb
@@ -28,8 +28,20 @@ describe Gitlab::Metrics::System do
   end
 
   describe '.cpu_time' do
-    it 'returns a Fixnum' do
-      expect(described_class.cpu_time).to be_an_instance_of(Fixnum)
+    it 'returns a Float' do
+      expect(described_class.cpu_time).to be_an_instance_of(Float)
+    end
+  end
+
+  describe '.real_time' do
+    it 'returns a Float' do
+      expect(described_class.real_time).to be_an_instance_of(Float)
+    end
+  end
+
+  describe '.monotonic_time' do
+    it 'returns a Float' do
+      expect(described_class.monotonic_time).to be_an_instance_of(Float)
     end
   end
 end