[dm-devel] Re: Too many I/O controller patches

[Dave Hansen <dave linux vnet ibm com>]

On Tue, 2008-08-05 at 11:28 +0200, Andrea Righi wrote:
> > Buffered write I/O is also related with cache system.
> > We must consider this problem as I/O control.
> 
> Agree. At least, maybe we should consider if an IO controller could be
> a valid solution also for these problems.

Isn't this one of the core points that we keep going back and forth
over?  It seems like people are arguing in circles over this:

Do we:
	1. control potential memory usage by throttling I/O
or
	2. Throttle I/O when memory is full

I might lean toward (1) if we didn't already have a memory controller.
But, we have one, and it works.  Also, we *already* do (2) in the
kernel, so it would seem to graft well onto existing mechanisms that we
have.

I/O controllers should not worry about memory.  They're going to have a
hard enough time getting the I/O part right. :)

Or, am I over-simplifying this?

-- Dave