Disable rugged auto-detect when Puma threads>1

If Puma is in use and Puma threads is more than 1, it is expected to
have performance lose by using Rugged patches, because of Rugged calls
does not release Ruby GVL while doing IO. So in this case, we will
ignore rugged automatic detect `can_use_disk?`.

lib/gitlab/git/rugged_impl/use_rugged.rb

@@ -8,9 +8,17 @@ module Gitlab
           feature = Feature.get(feature_key)
           return feature.enabled? if Feature.persisted?(feature)
 
+          # Disable Rugged auto-detect(can_use_disk?) when Puma threads>1
+          # https://gitlab.com/gitlab-org/gitlab/issues/119326
+          return false if running_puma_with_multiple_threads?
+
           Gitlab::GitalyClient.can_use_disk?(repo.storage)
         end
 
+        def running_puma_with_multiple_threads?
+          Gitlab::Runtime.puma? && ::Puma.cli_config.options[:max_threads] > 1
+        end
+
         def execute_rugged_call(method_name, *args)
           Gitlab::GitalyClient::StorageSettings.allow_disk_access do
             start = Gitlab::Metrics::System.monotonic_time

spec/lib/gitlab/git/rugged_impl/use_rugged_spec.rb

@@ -53,30 +53,46 @@ describe Gitlab::Git::RuggedImpl::UseRugged, :seed_helper do
       allow(Feature).to receive(:persisted?).with(feature_flag).and_return(false)
     end
 
-    it 'returns true when gitaly matches disk' do
-      expect(subject.use_rugged?(repository, feature_flag_name)).to be true
+    context 'when running puma with multiple threads' do
+      before do
+        allow(subject).to receive(:running_puma_with_multiple_threads?).and_return(true)
+      end
+
+      it 'returns false' do
+        expect(subject.use_rugged?(repository, feature_flag_name)).to be false
+      end
     end
 
-    it 'returns false when disk access fails' do
-      allow(Gitlab::GitalyClient).to receive(:storage_metadata_file_path).and_return("/fake/path/doesnt/exist")
+    context 'when not running puma with multiple threads' do
+      before do
+        allow(subject).to receive(:running_puma_with_multiple_threads?).and_return(false)
+      end
 
-      expect(subject.use_rugged?(repository, feature_flag_name)).to be false
-    end
+      it 'returns true when gitaly matches disk' do
+        expect(subject.use_rugged?(repository, feature_flag_name)).to be true
+      end
 
-    it "returns false when gitaly doesn't match disk" do
-      allow(Gitlab::GitalyClient).to receive(:storage_metadata_file_path).and_return(temp_gitaly_metadata_file)
+      it 'returns false when disk access fails' do
+        allow(Gitlab::GitalyClient).to receive(:storage_metadata_file_path).and_return("/fake/path/doesnt/exist")
 
-      expect(subject.use_rugged?(repository, feature_flag_name)).to be_falsey
+        expect(subject.use_rugged?(repository, feature_flag_name)).to be false
+      end
 
-      File.delete(temp_gitaly_metadata_file)
-    end
+      it "returns false when gitaly doesn't match disk" do
+        allow(Gitlab::GitalyClient).to receive(:storage_metadata_file_path).and_return(temp_gitaly_metadata_file)
 
-    it "doesn't lead to a second rpc call because gitaly client should use the cached value" do
-      expect(subject.use_rugged?(repository, feature_flag_name)).to be true
+        expect(subject.use_rugged?(repository, feature_flag_name)).to be_falsey
 
-      expect(Gitlab::GitalyClient).not_to receive(:filesystem_id)
+        File.delete(temp_gitaly_metadata_file)
+      end
 
-      subject.use_rugged?(repository, feature_flag_name)
+      it "doesn't lead to a second rpc call because gitaly client should use the cached value" do
+        expect(subject.use_rugged?(repository, feature_flag_name)).to be true
+
+        expect(Gitlab::GitalyClient).not_to receive(:filesystem_id)
+
+        subject.use_rugged?(repository, feature_flag_name)
+      end
     end
   end
 
@@ -99,6 +115,37 @@ describe Gitlab::Git::RuggedImpl::UseRugged, :seed_helper do
     end
   end
 
+  describe '#running_puma_with_multiple_threads?' do
+    context 'when using Puma' do
+      before do
+        stub_const('::Puma', class_double('Puma'))
+        allow(Gitlab::Runtime).to receive(:puma?).and_return(true)
+      end
+
+      it 'returns false for single thread Puma' do
+        allow(::Puma).to receive_message_chain(:cli_config, :options).and_return(max_threads: 1)
+
+        expect(subject.running_puma_with_multiple_threads?).to be false
+      end
+
+      it 'returns true for multi-threaded Puma' do
+        allow(::Puma).to receive_message_chain(:cli_config, :options).and_return(max_threads: 2)
+
+        expect(subject.running_puma_with_multiple_threads?).to be true
+      end
+    end
+
+    context 'when not using Puma' do
+      before do
+        allow(Gitlab::Runtime).to receive(:puma?).and_return(false)
+      end
+
+      it 'returns false' do
+        expect(subject.running_puma_with_multiple_threads?).to be false
+      end
+    end
+  end
+
   def create_temporary_gitaly_metadata_file
     tmp = Tempfile.new('.gitaly-metadata')
     gitaly_metadata = {