Merge branch 'ps/upload-pack-buffer-more-writes' into seen

Reduce system overhead "git upload-pack" spends relaying "git
pack-objects" output to the "git fetch" running on the other end of
the connection.

* ps/upload-pack-buffer-more-writes:
  upload-pack: reduce lock contention when writing packfile data
  upload-pack: fix debug statement when flushing packfile data

Author: gitster

upload-pack.c

@@ -270,6 +270,13 @@ static int relay_pack_data(int pack_objects_out, struct output_state *os,
 		}
 	}
 
+	/*
+	 * Make sure that we buffer some data before sending it to the client.
+	 * This significantly reduces the number of write(3p) syscalls.
+	 */
+	if (readsz && os->used < (LARGE_PACKET_DATA_MAX * 2 / 3))
+		return readsz;
+
 	if (os->used > 1) {
 		send_client_data(1, os->buffer, os->used - 1, use_sideband);
 		os->buffer[0] = os->buffer[os->used - 1];
@@ -457,11 +464,9 @@ static void create_pack_file(struct upload_pack_data *pack_data,
 	}
 
 	/* flush the data */
-	if (output_state->used > 0) {
+	if (output_state->used > 0)
 		send_client_data(1, output_state->buffer, output_state->used,
 				 pack_data->use_sideband);
-		fprintf(stderr, "flushed.\n");
-	}
 	free(output_state);
 	if (pack_data->use_sideband)
 		packet_flush(1);