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Date:      Mon, 4 Apr 2011 19:49:29 -0500
From:      Adam Vande More <amvandemore@gmail.com>
To:        Eitan Adler <lists@eitanadler.com>
Cc:        questions@freebsd.org, =?UTF-8?Q?Kristaps_K=C5=ABlis?= <kristaps.kulis@gmail.com>
Subject:   Re: tuning a system for a single user
Message-ID:  <BANLkTim6P2JmhnDRv=VvZ-Tgbx0vdAhi4Q@mail.gmail.com>
In-Reply-To: <BANLkTi=qJ0jUUM3uMT29PsVZ5XMKg-q9Uw@mail.gmail.com>
References:  <BANLkTinRYjgLraMkzz28vq0MENoj662hHQ@mail.gmail.com> <BANLkTinSGJmFKC2=-gKA_-VkwvXiO8JKgQ@mail.gmail.com> <BANLkTi=qJ0jUUM3uMT29PsVZ5XMKg-q9Uw@mail.gmail.com>

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On Mon, Apr 4, 2011 at 7:32 PM, Eitan Adler <lists@eitanadler.com> wrote:

> >  I believe no FreeBSD system is "single user". As root, daemon users,
> > system users, "nobody" is required for running system smoothly,
> > securely and easy, so scheduling is nessecary :)
>
> Obviously :-)
>
> I guess a better way to ask the question would be "for a desktop
> user". I see a lot tuning guides that show how to getting scalable
> systems - but few show potential changes for desktop users.
>

Some people have reported setting  kern.sched.preempt_thresh=224 yields a
smoother desktop experience, but I don't know exactly what that sysctl
actually changes, nor have I tried it myself.  I haven't experienced any
thing I would consider a problem with my FreeBSD desktop experience, but my
machines are relatively well powered.

If you're targeting something like an embedded system, I'd guess you'd find
the lowest hanging fruit by profiling a specific workload.  I imagine it
would start to get pretty complicated quite rapidly if you're in a complex
environment as what's good for one workload might be rather poor on another.

I might be way off in guessing your end goal, but what I would do on the
embedded system is develop a minimal baseline automated testing for each
subsystem(eg disk, network) then tie that into something like ministat(1)
and one of those graphing utilities.  Something like that could give you a
comprehensive picture of what changes to kernel, sysctl's, etc are doing to
performance.


-- 
Adam Vande More



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