posted by Eugenia Loli on Mon 8th Oct 2001 16:15 UTC

"Matt Dillon, VM and kernel FreeBSD team, Part IV"
7. From the technical point of view, how would you rate the Linux 2.4 kernel compared to BSD's?

Matt Dillon: I don't know enough about recent linux kernels to be able to rate them, nor would it be P.C. I do follow the VM work being done in Linux and in particular Rik van Riel's work. I think Linux is going through a somewhat painful transition as it moves away from a Wild-West/Darwinist development methodology into something a bit more thoughtful. I will admit to wanting to take a clue-bat to some of the people arguing against Rik's VM work who simply do not understand the difference between optimizing a few nanoseconds out of a routine that is rarely called verses spending a few extra cpu cycles to choose the best pages to recycle in order to avoid disk I/O that would cost tens of millions of cpu cycles later on. It is an attitude I had when I was maybe 16 years old... that every clock cycle matters no matter how its spent. Bull!

8. How is the "relationship" between the FreeBSD programmers and the OpenBSD/NetBSD ones? Do you share code, opinions, chatting regularly? Or all these BSD projects are completely independant to each other?

Matt Dillon: The BSD groups are like high school social circles. No, really! That's the best analogy I can think of! Many developers focus on just their little clique but a good chunk run in multiple circles. There are developers that maintain the same driver code across several BSD distributions. There are developers who focus their work in one BSD distribution but have ties to developers in others. If the work is interesting enough, such as the 'dirpref' work, developers that focus on coding in other BSD distributions will pick up the patch set and bring it in. That is how FreeBSD got the dirpref code. Kirk imported it from OpenBSD into FreeBSD-current and I MFC'd it to -stable after it had been proven out in -current.

In many respects this development methodology gives us the best of both worlds. Developers are free to focus on the distribution they are most familar with and if the work is interesting enough it gets several eyes from the other distributions who not only port the code in, but also review it. Testing can wind up occuring in all the distributions simultaniously and with something like 'dirpref', if someone finds a bug it will almost certainly wind up being fixed in the other distributions within a few days. Security bugs are independantly verified but often the fix is common to all the BSDs and no duplicate work need occur. There is constant borrowing going on between the BSDs and even between BSD and Linux, especially in regards to driver code.

9. What is your opinion on .NET and do you think that it may be possible that .NET change the OS "map" as we know it?

Matt Dillon: I believe .NET is Vapor. It's a marketing term dreamed up by Microsoft that will magically morph into whatever Microsoft eventually winds up delivering. MS announces grandiose ideas with cute catch phrases all the time, and as with any good vapor there is always some basis in truth (if only a little pinprick). The reality is a little different though... remember, these are the people that hyped windows-ME up the wazoo and all we got out of it was a speech-synthesized windows installation wizard! These are the people that called NT the unix-killer and told people it was as reliable as UNIX. .NOT is probably a more descriptive term for .NET. My guess is that it will turn into Microsoft-proprietary rent-a-service glue, and that it will introduce an order of magnitude more security issues then IIS.

10. Some say that FreeBSD has the best VM ever, whem compared to any other Operating System. Do you think that there is still space for improvement and are there still features to be added?

Matt Dillon: I think we made great progress stabilizing the VM system and working out performance issues related to machine scaling in the -4.x series of FreeBSD releases. The machines have proven to be great workhorses in a wide range of applications and are able to provide the long term stability and performance required by its users. Generally speaking, the technology behind the VM system is quite sound and does not need much more in the way of improvement. Obviously in -5.x we will be multi-threading pieces of it for SMPng, but the core algorithms appear to extend cleanly to MP and 64 bit platforms and we do not expect to have to make any fundamental changes. There is always room for improvement, of course! While we are likely to stand pat with the VM core in early 5.x releases, there is a great deal of work planned to improve the I/O and buffer cache subsystems a little later on. My personal goal is to eventually remove the buffer cache entirely or at least morph it into nothing more complex than an I/O staging subsystem.

Table of contents
  1. "Matt Dillon, VM and kernel FreeBSD team, Part I"
  2. "Matt Dillon, VM and kernel FreeBSD team, Part II"
  3. "Matt Dillon, VM and kernel FreeBSD team, Part III"
  4. "Matt Dillon, VM and kernel FreeBSD team, Part IV"
  5. "Itojun, NetBSD Core Team"
  6. "Theo de Raadt, OpenBSD Founder"
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