[ketozhang]

It's very interesting you mentioned ETL tasks. In ETL batch jobs, a unit in the batch is defined small enough to rarely be CPU bound; rather, as you mentioned, it is I/O bound. In what situation must you define a unit of work to be so heavily CPU bound? To me that's a smell for too large of a unit.

[heavyset_go]

I'm using ETL as shorthand for a "I wrote a script at home that parses my data and puts it in a database, and threads might save time" situation. I wouldn't reach for a thread pool for anything serious.