fetch: add trace2 instrumentation

Add trace2 regions to fetch-pack.c and builtins/fetch.c to better track
time spent in the various phases of a fetch:

* listing refs
* negotiation for protocol versions v0-v2
* fetching refs
* consuming refs

Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -1071,8 +1071,11 @@ static int check_exist_and_connected(struct ref *ref_map)
 static int fetch_refs(struct transport *transport, struct ref *ref_map)
 {
 	int ret = check_exist_and_connected(ref_map);
-	if (ret)
+	if (ret) {
+		trace2_region_enter("fetch", "fetch_refs", the_repository);
 		ret = transport_fetch_refs(transport, ref_map);
+		trace2_region_leave("fetch", "fetch_refs", the_repository);
+	}
 	if (!ret)
 		/*
 		 * Keep the new pack's ".keep" file around to allow the caller
@@ -1088,11 +1091,14 @@ static int consume_refs(struct transport *transport, struct ref *ref_map)
 {
 	int connectivity_checked = transport->smart_options
 		? transport->smart_options->connectivity_checked : 0;
-	int ret = store_updated_refs(transport->url,
-				     transport->remote->name,
-				     connectivity_checked,
-				     ref_map);
+	int ret;
+	trace2_region_enter("fetch", "consume_refs", the_repository);
+	ret = store_updated_refs(transport->url,
+				 transport->remote->name,
+				 connectivity_checked,
+				 ref_map);
 	transport_unlock_pack(transport);
+	trace2_region_leave("fetch", "consume_refs", the_repository);
 	return ret;
 }
 
@@ -1337,9 +1343,11 @@ static int do_fetch(struct transport *transport,
 			argv_array_push(&ref_prefixes, "refs/tags/");
 	}
 
-	if (must_list_refs)
+	if (must_list_refs) {
+		trace2_region_enter("fetch", "remote_refs", the_repository);
 		remote_refs = transport_get_remote_refs(transport, &ref_prefixes);
-	else
+		trace2_region_leave("fetch", "remote_refs", the_repository);
+	} else
 		remote_refs = NULL;
 
 	argv_array_clear(&ref_prefixes);

fetch-pack.c

@@ -382,6 +382,7 @@ static int find_common(struct fetch_negotiator *negotiator,
 		state_len = 0;
 	}
 
+	trace2_region_enter("fetch-pack", "negotiation_v0_v1", the_repository);
 	flushes = 0;
 	retval = -1;
 	if (args->no_dependents)
@@ -466,6 +467,7 @@ static int find_common(struct fetch_negotiator *negotiator,
 		}
 	}
 done:
+	trace2_region_leave("fetch-pack", "negotiation_v0_v1", the_repository);
 	if (!got_ready || !no_done) {
 		packet_buf_write(&req_buf, "done\n");
 		send_request(args, fd[1], &req_buf);
@@ -1378,7 +1380,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	enum fetch_state state = FETCH_CHECK_LOCAL;
 	struct oidset common = OIDSET_INIT;
 	struct packet_reader reader;
-	int in_vain = 0;
+	int in_vain = 0, negotiation_started = 0;
 	int haves_to_send = INITIAL_FLUSH;
 	struct fetch_negotiator negotiator;
 	fetch_negotiator_init(r, &negotiator);
@@ -1421,6 +1423,12 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			}
 			break;
 		case FETCH_SEND_REQUEST:
+			if (!negotiation_started) {
+				negotiation_started = 1;
+				trace2_region_enter("fetch-pack",
+						    "negotiation_v2",
+						    the_repository);
+			}
 			if (send_fetch_request(&negotiator, fd[1], args, ref,
 					       &common,
 					       &haves_to_send, &in_vain,
@@ -1444,6 +1452,9 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			}
 			break;
 		case FETCH_GET_PACK:
+			trace2_region_leave("fetch-pack",
+					    "negotiation_v2",
+					    the_repository);
 			/* Check for shallow-info section */
 			if (process_section_header(&reader, "shallow-info", 1))
 				receive_shallow_info(args, &reader, shallows, si);