DPL: improve instrumentation for the preProcessingCallbacks (#13104)

Author: ktf

Framework/Core/src/DataProcessingDevice.cxx

@@ -2321,6 +2321,7 @@ bool DataProcessingDevice::tryDispatchComputation(ServiceRegistryRef ref, std::v
                        *context.registry};
     ProcessingContext processContext{record, ref, ref.get<DataAllocator>()};
     {
+      O2_SIGNPOST_EVENT_EMIT(device, aid, "device", "Invoking preProcessingCallbacks");
       // Notice this should be thread safe and reentrant
       // as it is called from many threads.
       streamContext.preProcessingCallbacks(processContext);

Framework/Core/src/StreamContext.cxx

@@ -31,12 +31,17 @@ void StreamContext::preStartStreamCallbacks(ServiceRegistryRef ref)
 /// Invoke callbacks to be executed before every process method invokation
 void StreamContext::preProcessingCallbacks(ProcessingContext& pcx)
 {
+  O2_SIGNPOST_ID_FROM_POINTER(dpid, stream_context, &pcx);
+  O2_SIGNPOST_START(stream_context, dpid, "callbacks", "Starting StreamContext preProcessingCallbacks");
   for (auto& handle : preProcessingHandles) {
-    LOG(debug) << "Invoking preProcessingCallbacks for" << handle.service;
+    O2_SIGNPOST_ID_FROM_POINTER(cid, stream_context, handle.service);
+    O2_SIGNPOST_START(stream_context, cid, "callbacks", "Starting StreamContext::preProcessingCallbacks for service %{public}s", handle.spec.name.c_str());
     assert(handle.service);
     assert(handle.callback);
     handle.callback(pcx, handle.service);
+    O2_SIGNPOST_END(stream_context, cid, "callbacks", "Ending StreamContext::preProcessingCallbacks for service %{public}s", handle.spec.name.c_str());
   }
+  O2_SIGNPOST_END(stream_context, dpid, "callbacks", "Ending StreamContext preProcessingCallbacks");
 }
 
 /// Invoke callbacks to be executed after every process method invokation