Models not sharing DB connections. Performance issues?

[eluser]gon[/eluser]
Hi,

Do models share a single database connection?
I suspect they don't, as it's possible to pass each of them a different DB config.

When I used plain PHP, I would create a single connection that was used by every model.

Is there a way of doing this, and does it make sense in CI?

The reason is, obviously, performance. We expect a lot of hits on the website.
Prior to other strategies, I would like to optimize the core.

Regards.