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Kernel Fork For Big Iron?
Boone^ writes: "ZDNet is running an article on the future of Linux when used on Big Iron. Just a bit ago we read about running Linux on a large scale Alpha box, and SGI wants NUMA support in Linux so it can support their hardware configuration. The article talks about how memory algorithms used with 256GB machines would hamper performance on 386s with 8MB ram. So far Linus et al have been rejecting kernel patches that provide solutions for Big Iron scaling problems. How soon before a Big Iron company forks the kernel?"
Just as importantly, forks are probably necessary when a significant part of the user/developer base disagrees with the direction of the project. This usually implies that the forked version and the original version are aiming at solving different problems within the same vein. If the original project wants to continue in the original direction and some people want to use the source to solve a slightly different project, then they pretty much have to fork in order for the project to achieve its maximal result of being most useful to the most people.
This isn't a bad thing if it's done right. It's just that most of the big forks you hear of are at least partially the result of bitter, angry wars (OpenBSD anyone?). You don't hear that much about the ones which are completely amicable.
One of the issues that people seem to fail to realize is that Linus is not necessarily rejectiung the patches because of what they do, but how they are implemented. If patch code is submitted to Linus and the patch is going to make mataining that system difficult (read messy unmaintainable code) Linus will reject it. Linus also does not like large patches either. He likes bits and peices and clean fixes. Hey he started this whole thing, I think he has that right.
Another thing to think of is that ZDNet is a news network. Everyone has been saying that the kernel will fork and blah blah. There are already forks in the kernel but people just don't realize this.
Redhat kernels: Have you ever tried to apply a patch to a stock redhat kernel? I know that since RH5.2 they ship the Linux kernel with there own patches.
SuSE kernels: Last SuSSE I installed (5.3) had both a stock Linux kernel and a custom SUSE kernel with custom SuSE patches.
Corel: never tries them but they patched kde and made it hard to compile other kde software with there distro.
Point? There are already forks in the Linux community, yet it goes on. That is the whole thing about open source. There can be forks. If an idea is good it gets into the mainstream kernel. But these 'forks' need to be tried first and become tested and cleand up in such a maner that they can exist with the rest of the linux kernel.
If you think that everyone is running P200 or P500 or GigHz machines you are wrong. I am sure that there are lots of people out there that are running old 386 / 486 with Linux as routers firewalls, etc. After all you do not need a superfast machine for a firewall if all you are going to firewall is 3 or 4 other machines.
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I am constantly putting Linux onto old hardware. Need a quick, dirty, and cheap NAT box? Throw Linux on a DX2/66.
MP3 file server for the geeks in IT? Throw in a big drive, but a 486 will do.
Hell, my company's web server is running on a low end PII, and I think it's a horrendous waste! It could be doing *so* much more.
Linux is a UNIX for cheap Intel hardware first. That's where its roots are, and I don't see why it should sacrifice its roots for big iron that can quite happily run a UNIX designed for big iron.
Neither does Linus, apparently.
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It depends on how pervasive the code changes have to be. If it involves #ifdeffing every single file, then it's going to be very difficult to maintain that, and it's going to be very unlikely that the maintainers of the project are going to allow that feature to remain part of the major distribution.
That problem is a dual-edged sword. It also means that maintaining one big patch is a complete nightmare. Every version of the kernel that comes out has to be separately patched, with two important considerations:
- The code which needs to be inserted has to be reinserted. If this is all separate files, that's easy, but if it's not that's a complete nightmare. And the code to call into that separate file is then a nightmare.
- Any changes which have broken the patch have to be investigated and possibly changed. If you're working on filesystem patches, for example, someone working on the core fs work may have broken your patch without your knowing it, because they're not including your code in their coding/debugging process. So every time there's a change to the kernel, you have to figure out whether that change will potentially break your work.
The only way to resolve the second is to keep the patch inside the actual kernel, so that the authors of the rest of the system are aware of it, and will either try their best not to break it, or will do first-round of changing the new functionality to work with their changes.Basically, it comes down to how pervasive the work has to be. If it's a really pervasive change which touches on almost everything, then the only option from a software engineering perspective is a fork. Anything else is being done from a feel-good PR perspective, because it just doesn't make any sense from a technical perspective to try to maintain a huge patch that covers everything.
This makes it sound like Linus has been rejecting them because they provide solutions for Big Iron scaling problems. Having read kernel traffic and the linux-kernel list enough, this statement looks immediately suspicious. I have never seen Linus ever purposely reject a patch that's an all-around good fix for a problem. Usually it's "Well, Linus rejected my patch even though it does all this cool stuff and fixes all these problems, so it's probably because he just doesn't like such-and-such feature/platform/interface" and then Linus replies, "no, I rejected them because you're a dumbass and your patch sucked."
The link to the SGI page somewhat confirms this:
I just kinda heavily doubt that Linus wouldn't want awesome NUMA support if the potential was there. My best bet is that the people pushing for it just aren't on exactly the same wavelength as Linus (is anyone?) and it's slowing down progress.
Another quote that points in this direction
I don't think Linus mean any solution, just the solutions presented to him.
Yes, it is nice that it will still run on a 386, but there are other factors to consider:
1. Earlier platforms generally had no CD-ROM. Most Linux distros (except for fringe distros) come on CD-ROMs. Most people do not want to buy a CD-ROM for their 386, 486s. There are places that offer small "floppy-disk-sized" Linux distros, but they are obviously chopped. 1400K on a 500MB HDD.
2. Earlier machines usually had a 5 1/4" floppy disk, until the late 486s started really using 3.5" floppies. Most people are not going to spend money and time ripping out an old floppy.
3. Earlier machines had RAM limitations, aside from the fact that no one wants to really waste the money on putting more EDO memory into an obsolete machine.
4. Some earlier machines had fscked BIOSes, aside from Y2K-unfriendly BIOSes; Most people will not research whether the particular BIOS is okay to determine whether or not to spend money on the first three items.
5. Earlier machines had ISA, EISA, etc. Oh, what, you want to run GNU/Linux in something other than CGA?
6. Earlier network cards are not all supported to get around many of these limitations... I tried to get around not having a CD or a 3.5" floppy in an old 486 by using some sort of older ISA-based network card.
Obviously, there are many issues to consider before nodding one's head to allow Linus to try to preserve performance in ancient boxen for nostalgic purposes.
Lucas
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Even in the cases where Linus has outright rejected BigIron patches, nothing stops a hardware vendor from patching the source after the fact - almost every major Linux distribution does this now for x86/ppc/sparc etc. (NFSv3 is a great example)
I wouldn't be shocked if the stretching of boundaries that comes from:
- "Big Iron" changes, as well as
- Embedded System changes
winds up turning into there being some clear demands for forking.The fundamental problem with a fork comes in the code that you'd ideally like to be able to share between the systems. Device drivers float particularly to mind.
After a 2-way fork, it becomes necessary to port device drivers to both forks, which adds further work.
And if a given driver is only ported to one fork, and not the other, can it correctly be said that
or do we need to be forever vague about that?If you're not part of the solution, you're part of the precipitate.
Forks are usually justified only if the original maintainer pollutes the source with hacks or changes the license.
Perhaps the time has come to fork the older machines.. Few of us run Linux on anything less powerful than a Pentium, and even fewer on a 486.
I don't know, it depends on where the split of cost/benefit falls.. ZD doesn't say...
`Sides, having a Compaq/SGI/IBM 'approved' kernel patch doesn't hurt much..
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This was bound to happen sooner or later. The Linux kernel's flexibility is being taken to the limit, and people are forgetting the easiest way to improve performance for their particular rig: Customize your kernel! You can add all the code in the universe, and then you pick and choose the particular things you need or don't need! Say I run a 486/25 with 16 MB RAM as an IP Masq router. The hard drive is an old IDE with 600 megs of space. I have two network cards, and that's about it. Do I need SCSI support? Do I need to support joysticks, X, Pentiums, AX.25, or anything else? No! I compile a kernel specifically to run the IP Masq, and run it well. My P100 laptop, on the other hands needs a bit more. I use it for packet, so I need AX.25. It uses PCMCIA, so PCMCIA support needs to go in. I use XWS to run Netscape and the GIMP, so I need graphics. But, my HD is not SCSI. I yank out SCSI. My CPU is subject to the 0xf00f bug, so that gets included. I brew a custom kernel, and boot time is a lot shorter. My big-rig is a C433. I need just about everything, as I have a 3dfx card for Quake3; XWS; a SCSI scanner; and a connection to my Packet base station. I optimize compilation for the higher-end computers. I plan on getting a Cube from Apple and putting SuSE on it. Again, by optimizing the options I optimize my system. Get the point? If you want a once-size-fits-all kernel, use Windows. If you want a kernel which can be adjusted for your particular and peculiar environment, use Linux and customize your kernel! Now, for my laptop.
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