"Simon Marlow" writes:

...

To fix these problems you have to think carefully about strictness and

demand in your

...

program. For memory we have heap profilers to help out, but we don't have I/O descriptor profilers for lazy I/O!

Surely I/O descriptors are just a type of heap-value, and as such can be profiled in the normal way (producer, retainer, etc), just like any other heap construction?

File descriptors are held in the kernel, not the heap. Hmmm, I suppose you could track Handles, which notionally "hold on to" a file descriptor, but it's not completely reliable because a Handle will be held by a finalizer for an unspecified period of time before the descriptor is released. In practice it might not be a serious problem unless there are lots of other threads. Cheers, Simon