Spring deferredResult performance issue with Okhttp - spring

Question

I'm trying to test a basic blocking and non-blocking API controller that stream OkHttp response like following:
#SpringBootApplication
public class HttpProxyServiceApplication {
public static void main(String[] args) {
SpringApplication.run(HttpProxyServiceApplication.class, args);
}
#Bean
public OkHttpClient okHttpClient() {
return new OkHttpClient();
}
#RestController
#RequestMapping(path = "/test")
public static class TestController {
private static final String URL = ...;
#Autowired
private OkHttpClient client;
#RequestMapping(method = RequestMethod.GET, path = "blocking")
public void blocking(HttpServletResponse httpServletResponse) throws IOException {
Request request = new Request.Builder()
.url(URL)
.build();
try (ResponseBody body = client.newCall(request).execute().body()) {
StreamUtils.copy(body.byteStream(), httpServletResponse.getOutputStream());
}
}
#RequestMapping(method = RequestMethod.GET, path = "non-blocking")
public DeferredResult<ResponseEntity<?>> nonBlocking() {
Request request = new Request.Builder()
.url(URL)
.build();
DeferredResult<ResponseEntity<?>> deferredResult = new DeferredResult<>();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(Request request, IOException e) {
ResponseEntity<Void> responseEntity =
new ResponseEntity<>(HttpStatus.SERVICE_UNAVAILABLE);
deferredResult.setResult(responseEntity);
}
#Override
public void onResponse(Response response) throws IOException {
ResponseEntity<InputStreamResource> responseEntity =
new ResponseEntity<>(new InputStreamResource(response.body().byteStream()),
HttpStatus.ACCEPTED);
deferredResult.setResult(responseEntity);
}
});
return deferredResult;
}
}
}
Important thing: I want to stream result ! I don't want to save whole result in memory. That's why for non-blocking I created a ResponseEntity<InputStreamResource>.
However using basic JMeter script that crawls on both API, the non-blocking is really slower than the blocking one
500 threads
Blocking result:
Non-blocking result:
There is any reason?
Update 1:
New test
#RequestMapping(method = RequestMethod.GET, path = "non-blocking-2")
public DeferredResult<InputStreamResource> nonBlockingBlocking() throws IOException {
Request request = new Request.Builder()
.url(URL)
.build();
DeferredResult<InputStreamResource> deferredResult = new DeferredResult<>();
deferredResult.setResult(new InputStreamResource(client.newCall(request).execute().body().byteStream()));
return deferredResult;
}
As similar result as full blocking. So I don't think is performance issue directly come from DeferredResult.