SMP (Was: Why did you choose DragonFly?)

Przemysław Pawełczyk pp_o2 at
Mon Sep 20 15:52:55 PDT 2010

On Mon, 20 Sep 2010 16:21:19 -0600
"Samuel J. Greear" <sjg at> wrote:

> 2010/9/20 Przemysław Pawełczyk <pp_o2 at>:
> > On Mon, 20 Sep 2010 13:33:28 -0600
> > "Samuel J. Greear" <sjg at> wrote:
> >
> >> This mail is intended for the infrequent responders and lurkers on
> >> the list just as much as the regular posters.
> >>
> >> What has drawn you to use the DragonFly BSD operating system and/or
> >> participate in its development by following this list? Technical
> >> features, methodologies, something about the community? I suspect
> >> the HAMMER filesystem to be the popular choice, but what other
> >> features affect or do you see affecting your day to day life as an
> >> administrator, developer, or [insert use case here], now or in the
> >> future?
> >>
> >
> > Hi Sam,
> >
> > A question for a question.
> >
> > Why _no one_ answered my question concerning DF BSD contained in my
> > post:
> >
> >
> > What did I do wrong?
> >
> > I thought them over before I gathered enough temerity to ask here
> > for anything.
> >
> > Why do you ask me -"a lurker" - to answer your questions when you
> > (plural) are treating "the lurkers" that way?
> >
> > Regards
> >
> > --
> > Przemysław Pawełczyk (P2O2) [pron. Pshemislav Paveltchick]
> >, pp_o2 at
> >
> I will try to answer here and now.
> The purpose of my question(s) is because I believe DragonFly BSD is
> not adequately represented in the easily accessible (main page and
> pages directly linked from it) literature on our website. I would like
> to fix this so that questions like yours need not arise in the future.
> As a first step I wanted to learn what people like about DragonFly and
> what keeps people using this OS and participating in the community so
> that I could expand on those points.
> DragonFly BSD is not necessarily targeted -to- SMP, rather it supports
> SMP and adopts a slightly different model than other mainstream
> operating systems. Most OS kernels use primarily "hard" locks in the
> form of mutexes and spinlocks. DragonFly prefers "soft" locks in the
> form of tokens and, even better, lockless algorithms. I do not believe
> anyone is ready to make any bold claims about our current SMP
> performance. However, I do believe many developers would claim that
> even though we may be a bit behind in performance today our
> model/methodology positions us well for the future.
> Modern hardware should be pretty well supported, if FreeBSD supports
> it then generally so should we and if we don't it is likely not too
> much work to port that support over. Matt Dillon just brought up
> DragonFly on a new AMD 880-series-based motherboard with a 6-core CPU
> and that is apparently working quite well.
> HAMMER is definitely a competitor to ZFS, although not in terms of
> volume management. We have LVM for that, but currently it does not
> support many of the targets one might expect (None of the real RAID
> levels). HAMMER is partly MPSAFE and many of the subsystems above it
> are also partially or fully MPSAFE, performance on multiple CPU's
> should be quite good from the point of view of the filesystem.


Thanks for your reply.

There are numerous examples of complex and simple storage/backup
methods. There are a lot of home networks with modern PCs having TB

A lot of people ask about and got excited on the three characters ZFS.

Do you see any real advantage and applications for HAMMER for such
home configurations? With emphasis on snapshots being stored on second

Answering your general questions:

What pulled me into the domain of DF is innovation. Then practical
methods to squeeze out from present PCs 100% of their processing
powers. And - the new type of kernel which would be able (?) to push
us closer to the Holy Grail of raw processing - the microkernels or
the kernel that is not monolithic (whatever it would mean).

BTW. I looked over packages. It seems to me the applications are not
"fresh". Wait a minute - I think that OpenBSD is more up-to-date
concerning the packages.


Przemysław Pawełczyk (P2O2) [pron. Pshemislav Paveltchick], pp_o2 at
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