1. recover to w mode to fopen the perf log file. 2. enrich comments

runtime/src/main.c

@@ -222,7 +222,7 @@ runtime_configure()
 	char *runtime_sandbox_perf_log_path = getenv("SLEDGE_SANDBOX_PERF_LOG");
 	if (runtime_sandbox_perf_log_path != NULL) {
 		printf("\tSandbox Performance Log: %s\n", runtime_sandbox_perf_log_path);
-		runtime_sandbox_perf_log = fopen(runtime_sandbox_perf_log_path, "a+");
+		runtime_sandbox_perf_log = fopen(runtime_sandbox_perf_log_path, "w");
 		if (runtime_sandbox_perf_log == NULL) { perror("sandbox perf log"); }
 		fprintf(runtime_sandbox_perf_log, "id,function,state,deadline,actual,queued,initializing,runnable,"
 		                                  "running,blocked,returned,memory\n");

runtime/src/worker_thread.c

@@ -54,8 +54,9 @@ worker_thread_main(void *argument)
 
 	scheduler_runqueue_initialize();
 
-	/* Initialize memory logging */
-	mem_log_init2(1024*1024*1024, runtime_sandbox_perf_log);
+	/* Initialize memory logging, set 100M memory for logging */
+	//mem_log_init2(1024*1024*1024, runtime_sandbox_perf_log);
+	mem_log_init2(1024, runtime_sandbox_perf_log);
 	/* Initialize Completion Queue */
 	local_completion_queue_initialize();