How To Determine Which Network Programming Architecture Is Being Used

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Most program documentation remains vague about which network programming architecture is used. Since the architecture is the single strongest determinant of performance under load, you need a way to find out. Below are techniques you can use snoop on an application, even if you do not have access to the source code. First, you must set up a load-creating situation, with at least 200 simultaneous tasks. Then, examine how the process is running with various tools:

Linux

• Run top

• One-process-per-task — Many processes running, all with a different amount of memory use.

• One-thread-per-task — Many processes running, all with the same amount of memory use, and the number of processes changes over time.

• One-thread-many-tasks (one thread) — A single process running.

• One-thread-many-tasks (several threads) — Many processes running, all with the same amount of memory use, and the number of processes is less than 100.

Solaris

• Run ps -efL. The “NLWP” column indicates how many “lightweight processes” are running inside each process, and lists each LWP in a separate row.

• One-process-per-task — ps -efL reports multiple copies of your application, but each has a different process ID, then the application uses the process-per-task approach.

• One-thread-per-task — Multiple processes reported by ps -efL for your application. If all have the same process ID, and the number of copies changes over time, then the application uses the one-thread-per-task (multi-threaded) approach.

• One-thread-many-tasks (one thread) — A single process reported.

• One-thread-many-tasks (several threads) — Multiple copies of your application reported by ps - efL, all running copies of your application have the same process ID, and the number of copies is less than 100.

Windows 2000 and NT

• Use Task Manager to view active tasks and perfmon.exe to view the number of threads in the running task.

• One-process-per-task — Task Manager shows approximately one process per running task.

• One-thread-per-task — perfmon.exe shows approximately one thread per running task.

• One-thread-many-tasks (one thread) — One process, one thread.

• One-thread-many-tasks (several threads) — Task Manager shows one process; perfmon.exe shows less than 100 threads.

Alternative Snooping Technique: Trace the System Calls

• Use strace (on Linux) or truss (on Solaris and FreeBSD) to display the application’s system calls.

• grep for calls to “select” or “poll”, which usually indicate asynchronous operations. Poll() is more efficient than select() with large numbers of connections.

• grep for calls that start with aio (which stands for Asynchronous I/O) or lio (List I/O). These calls are a likely sign of a sophisticated asynchronous architecture. Examples: aio_write(), aio_read(), lio_listio().

• grep for calls that start with “pthread” or “thr_” (on Solaris), which indicates some amount of multi-threading. If a new task always causes a call the pthread_create(), then the “one-thread-per-task” design is being used.