title: How do I tell what a Linux process is waiting for?
body: <p>I'm trying to track down the cause of performance bottlenecks in an application I'm debugging under Linux. The various processes involved seem to spend a lot of their time blocking on I/O requests, and I was wondering if anybody knew any Linux tricks that let you see <em>why</em> a particular process is blocked/what resource it's waiting for? Is there anything useful in <code>/proc</code> for instance?</p>