How to profile wall-clock time?

In my program, real time duration is sometimes as much as 3 times that of cpu time. This is a single thread application that does a lot of memory allocation and NFS base read/write. So my doubt is that it is either mem-swap or NFS read-write that is slowing things down. For example, the following is the output of /usr/bin/time a.out 2165.32user 64.93system 6036.33elapsed Is there any profiling tool for real time? I know and have used multiple tools for cpu time profiling, but am not sure if there is anything that can help and point out NFS / mem-swap or any other wall clock slowdowns. My program is written in C++ **EDIT** : /usr/bin/time gives me a summary at the end - I am not looking for that. I am looking for a way to correlate the real-time consumption during specific program blocks of my application. A profiler like collect/gprof that can tell me things like - the area where most context switches are happening due to waits. - specific functions where NFS access is happening. Since my system is dedicated, I am not worried about other processes that might impact these profiles.