Re: Leaving the Desktop Market

On 1 Apr 2014, at 08:11, Jordan Hubbard <jkh@mail.turbofuzz.com> wrote:

> 1. Power.  As you point out, being truly power efficient is a complete to=
p-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 act=
ually involves a fair amount of micro architecture knowledge), you need a k=
ernel scheduler that is power management aware, you need a process manageme=
nt system that runs as few things as possible and knows how to schedule thi=
ngs during package wake-up intervals, you need timers to be coalesced at th=
e level where applications consume them, the list just goes on and on.  It=
=92s 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.

Just a small note here: Improving power management is something that the Co=
re 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 intere=
sted in doing the work.  If you know of anyone in either category then plea=
se 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 f=
or anyone interested in working on this, and I believe your former employer=
 had some expertise in this area.

Of course, no matter how good the base system becomes at power management, =
we still can't prevent stuff in ports running idle spinloops.  We can, howe=
ver, provide tools that encourage power-efficient design.  For example, cur=
rently hald wakes up every 30 seconds and polls the optical drive if you ha=
ve 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.  If you have a lapto=
p with an optical drive, this is really bad for power usage.  =

David

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