KernelTrap - flames

Quote: If You Wrote Code, I'd Be Worried

Jeremy — Thu, 17 Jan 2008 13:24:03 +0000

"I'm so glad you have nothing better to do than troll, if you actually wrote code I'd be worried it might get into something people used."

SFLC on Atheros Driver Issue

Jeremy — Sun, 16 Sep 2007 14:42:30 +0000

As the Atheros driver issue continues to simmer on the OpenBSD -misc mailing list and the Linux Kernel mailing list, with debate continuing over when the license of source code can be altered or added to, Eben Moglen made a statement for the Software Freedom Law Center. He began by defending their own actions, "it might be useful to recall the first stage of this process, when OpenBSD developers were accused of misappropriating Atheros code, and SFLC investigated and proved that no such misappropriation had occurred? Wild accusations about our motives are even more silly than they are false." He went on to acknowledge, "we understand that attribution issues are critically important to free software developers; we are accustomed to the strong feelings that are involved in such situations. In the fifteen years I have spent giving free legal help to developers throughout the community, attribution disputes have been, always, the most emotionally charged." He added that the SFLC would be making no further statements until their work on this matter was complete, noting:

"Also, and again for the last time, let me state that SFLC's instructions from its clients are to establish all the facts concerning the development of the current relevant code (which means the painstaking reconstruction of several independent and overlapping lines of development, including forensic reconstruction through line-by-line code reviews where version control system information is not available), as well as to resolve all outstanding legal issues, and to make policy recommendations, if possible, that would result in all projects, under both GPL and ISC, having full access to all code on their preferred terms, on an *ongoing* basis, with full respect for everyone's legal rights. We continue to believe those policy goals are achievable in this situation. The required work has been made more arduous because some people have chosen not to cooperate in good faith. But we will complete the work as soon as we can, and we will, as Mr Garvik says, follow the community's practice of complete publication, so everyone can see all the evidence."

CFS Digressions

Jeremy — Fri, 14 Sep 2007 09:25:57 +0000

"In the patch you really remove _a_lot_ of stuff," commented Roman Zippel in his reaction to Ingo Molnar's latest updates to the Completely Fair Scheduler. Roman has been consistently critical of Ingo's efforts, asking questions and criticizing Ingo's feedback. He continued, "you also removed a lot of things I tried to get you to explain them to me. On the one hand I could be happy that these things are gone, as they were the major road block to splitting up my own patch. On the other hand it still leaves me somewhat unsatisfied, as I still don't know what that stuff was good for."

Ingo replied to Roman's technical concerns, and pointed out that he'd been traveling for the recent kernel summit, adding, "I bent backwards trying to somehow get you to cooperate with us (and I still haven't given up on that!) - instead of you disparaging CFS and me frequently :-(". Willy Tarreau took a more critical stance, calling into question Roman's motives. He noted that he had been impressed by Roman's original review of the scheduler, but disappointed as the discussion seemed to degenerate, "it's the way you're trying to prove Ingo is a bastard and that you're a victim. But if we just re-read a few pick-ups of your mails since Aug 1st, its getting pretty obvious that you completely made up this situation." Kyle Moffett added, "I get the impression that Ingo re-implemented some ideas that you had because you refused to do so in a way that was acceptable for the upstream kernel. How exactly is this a bad thing?"

Linux: Discussing the Really Fair Scheduler

Jeremy — Mon, 03 Sep 2007 21:18:02 +0000

Ingo Molnar reviewed Roman Zippel's Really Fair Scheduler code, suggesting that much of the work was similar to that which was being done by Peter Zijlstra, "all in one, we don't disagree, this is an incremental improvement we are thinking about for 2.6.24. We do disagree with this being positioned as something fundamentally different though - it's just the same thing mathematically, expressed without a "/weight" divisor, resulting in no change in scheduling behavior. (except for a small shift of CPU utilization for a synthetic corner-case)"

Roman was not impressed with Ingo's review, asking, "did you even try to understand what I wrote?" He continued, "while Peter's patches are interesting, they are only a small step to what I'm trying to achieve." Regarding performance and code-quality concerns with his patch he added, "I explicitly said that my patch is only a prototype, so I haven't done any cleanups and tuning in this direction yet, so making any conclusions based on code size comparisons is quite ridiculous at this point. The whole point of this patch was to demonstrate the algorithmic changes, not to demonstrate a final and perfectly tuned scheduler."

Linux: Avoiding Pluggable Designs

Jeremy — Mon, 30 Jul 2007 18:37:00 +0000

Discussion continues regarding the choice to merge the CFS scheduler into the upcoming 2.6.23 kernel. A recent thread looked at the possibility of having merged the plugsched code to allow for both the CFS and SD schedulers to coexist in the mainline kernel at the same time, thereby avoiding the recent flamewars. Linus Torvalds pointed to the ManagementStyle documentation and acknowledged that while it's better to avoid flamefests when possible, "at the same time, I don't like playing politics with technology. The kernel is a technical project, and I make technical decisions. So I absolutely detest adding code for 'political' reasons."

As to the technical reason why he wasn't interested in making the CPU scheduler pluggable, Linus explained, "this is one approach, but it's actually one that I personally think is often the worst possible choice. Why? Because it ends up meaning that you never get the cross-pollination from different approaches (they stay separate 'modes'), and it's also usually really bad for users in that it forces the user to make some particular choice that the user is usually not even aware of." He went on to note, "I personally think that it's much better to find a setup that works 'well enough' for people, without having modal behaviour. People complain and gripe now, but what people seem to be missing is that it's a journey, not an end-of-the-line destination. We haven't had a single release kernel with the new scheduler yet". He added, "this, btw, has nothing to do with schedulers per se. We have had these exact same issues in the memory management too - which is a lot more complex than scheduling".

Linux: Linus On CFS vs SD

Jeremy — Sat, 28 Jul 2007 05:10:42 +0000

"People who think SD was 'perfect' were simply ignoring reality," Linus Torvalds began in a succinct explanation as to why he chose the CFS scheduler written by Ingo Molnar instead of the SD scheduler written by Con Kolivas. He continued, "sadly, that seemed to include Con too, which was one of the main reasons that I never [entertained] the notion of merging SD for very long at all: Con ended up arguing against people who reported problems, rather than trying to work with them." He went on to stress the importance of working toward a solution that is good for everyone, "that was where the SD patches fell down. They didn't have a maintainer that I could trust to actually care about any other issues than his own." He then offered some praise to Ingo, "as a long-term maintainer, trust me, I know what matters. And a person who can actually be bothered to follow up on problem reports is a *hell* of a lot more important than one who just argues with reporters." Linus went on to note a comparison between the two schedulers:

"I realize that this comes as a shock to some of the SD people, but I'm told that there was a university group that did some double-blind testing of the different schedulers - old, SD and CFS - and that everybody agreed that both SD and CFS were better than the old, but that there was no significant difference between SD and CFS."

Linux: Linus on the GPL, BSD, Tivo and the FSF

Jeremy — Fri, 15 Jun 2007 14:11:18 +0000

A lengthy debate that began with a suggestion to dual license the Linux kernel under the GPLv2 and the GPLv3 [story] continues on the Linux Kernel Mailing List. Throughout the ongoing thread Linux creator Linus Torvalds has spoken out on the GPLv2, the upcoming GPLv3, the BSD license, Tivo, the Free Software Foundation, and much more. During the discussion, he was asked we he chose the GPLv2 over the BSD license when he's obviously not a big fan of the FSF. Linus explained:

"Because I think the GPLv2 is a great license. And I don't like the FSF's radical world-view, but I am able to separate the license (the GPLv2) from the author and source of the license (rms and the FSF). Why do people always confuse the two? The GPLv2 stands on its own. The fact that I disagree with the FSF on how to act has _zero_ relevance for my choice of license.

"[...] But for a project I actually care about, I would never choose the BSD license. The license doesn't encode my fundamental beliefs of 'fairness'. I think the BSD license encourages a 'everybody for himself' mentality, and doesn't encourage people to work together, and to merge."

Linux: Dual-Licensing the Kernel

Jeremy — Tue, 12 Jun 2007 10:19:45 +0000

"I was impressed in the sense that it was a hell of a lot better than the disaster that were the earlier drafts," Linus Torvalds explained in reply to a comment suggesting that he was impressed with the final draft of the GPLv3. He went on to add, "I still think GPLv2 is simply the better license." The discussion began with a suggestion that the Linux kernel be dual-licensed GPLv2 and GPLv3. Linus noted, "I consider dual-licensing unlikely (and technically quite hard), but at least _possible_ in theory. I have yet to see any actual *reasons* for licensing under the GPLv3, though. All I've heard are shrill voices about 'tivoization' (which I expressly think is ok) and panicked worries about Novell-MS (which seems way overblown, and quite frankly, the argument seems to not so much be about the Novell deal, as about an excuse to push the GPLv3)." In a followup email, Linus added:

"Btw, if Sun really _is_ going to release OpenSolaris under GPLv3, that _may_ be a good reason. I don't think the GPLv3 is as good a license as v2, but on the other hand, I'm pragmatic, and if we can avoid having two kernels with two different licenses and the friction that causes, I at least see the _reason_ for GPLv3. As it is, I don't really see a reason at all."