Re: workqueue thing

Ingo Molnar
2009-12-23T08:50:38Z

* Tejun Heo <tj@kernel.org> wrote:

> Hello,
>
> On 12/23/2009 05:37 PM, Ingo Molnar wrote:
> >> Sure, fair enough but there's also a different side. It'll allow much
> >> easier implementation of things like in-kernel media presence polling (I
> >> have some code for this but it's still just forming) and per-device. It
> >> gives a much easier tool to extract concurrency and thus opens up new
> >> possibilities.
> >>
> >> So, anyways, alright, I'll go try some conversions.
> >
> > Well, but note that you are again talking performance. Concurrency
> > _IS_ performance: either in terms of reduced IO/app/request latency
> > or in terms of CPU utilization.
>
> I wasn't talking about performance above. Easiness or flexibility to
> extract concurrency opens up possibilities for new things or easier ways of
> doing things. It affects the design process. You don't have to jump
> through hoops for concurrency management and removing that restriction
> results in lower amount of convolution and simplifies design.

Which is why i said this in the next paragraph:

> > ( Plus reduction in driver complexity can be measured as well, in the
> > diffstat space.)

A new facility that is so mysterious that it cannot be shown to have any
performance/scalability/latency benefit _nor_ can it be shown to reduce driver
complexity simply does not exist IMO.

A tangle benefit has to show up _somewhere_ - if not in the performance space
then in the diffstat space (and vice versa) - that's all what i'm arguing.

Ingo