On Tue, Apr 01, 2014 at 08:38:28AM +0100, David Chisnall wrote:
> On 1 Apr 2014, at 08:11, Jordan Hubbard <j...@mail.turbofuzz.com> wrote:
> > 1. Power. As you point out, being truly power efficient is a complete
> > top-to-bottom engineering effort and it takes a lot more than just trying
> > to idle the processor whenever possible to achieve that. You need to
> > optimize all of the hot-spot routines in the system for power efficiency
> > (which actually involves a fair amount of micro architecture knowledge),
> > you need a kernel scheduler that is power management aware, you need a
> > process management system that runs as few things as possible and knows
> > how to schedule things during package wake-up intervals, you need timers
> > to be coalesced at the level where applications consume them, the list
> > just goes on and on. It's a lot of engineering work, and to drive that
> > work you also need a lot of telemetry data and people with big sticks
> > running around hitting people who write power-inefficient code. FreeBSD
> > has neither.
Thanks Jordan, this is an excellent elaboration on why exactly we're behind
on the "green" lane, and on power-neglective FreeBSD development overall.
> Just a small note here: Improving power management is something that the
> Core Team and the Foundation have jointly identified as an important goal,
> in particular for mobile/embedded scenarios. We're currently coordinating
> potential sponsors for the work and soliciting proposals from people
> interested in doing the work. If you know of anyone in either category
> then please drop either me, core, or the Foundation an email.
> Some things have already seen progress, for example Davide's calloutng work
> includes timer coalescing, but there are still a lot of, uh, opportunities
> for improvement. The Symbian EKA2 book has some very interesting detail on
> their power management infrastructure, which would be worth looking at for
> anyone interested in working on this, and I believe your former employer
> had some expertise in this area.
Now that's something I'm glad to hear. It would be cool if FreeBSD gained
some power-efficient software that run smoothly together with hardware (and
laptops in particular) developed by Jordan's former employer. ;-)
> For example, currently hald wakes up every 30 seconds and polls the optical
> drive if you have one. Why? Because there's no devd event when a CD is
> inserted, so the only way for it to get these notifications is polling.
I'm surprised to find out that our devd(8) does not emit some event on CD
insertion. On the other, if by "hald" you mean the one installed by the
`sysutils/hal' port, I've personally never run it, and do not recommend it
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