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Con Kolivas Returns, With a Desktop-Oriented Linux Scheduler
myvirtualid writes "Con Kolivas has done what he swore never to do: returned to the Linux kernel and written a new — and, according to him — waaay better scheduler for the desktop environment. In fact, BFS appears to outperform existing schedulers right up until one hits a 16-CPU machine, at which point he guesses performance would degrade somewhat. According to Kolivas, BFS 'was designed to be forward looking only, make the most of lower spec machines, and not scale to massive hardware. i.e. [sic] it is a desktop orientated scheduler, with extremely low latencies for excellent interactivity by design rather than 'calculated,' with rigid fairness, nice priority distribution and extreme scalability within normal load levels.'"
No. They would be crazy to use this scheduler anyway since it won't scale to
their 4096 cpu machines. The only way is to rewrite it to work that way, or
to have more than one scheduler in the kernel. I don't want to do the former,
and mainline doesn't want to do the latter. Besides, apparently I'm a bad
maintainer, which makes sense since for some reason I seem to want to have
a career, a life, raise a family with kids and have hobbies, all of which
have nothing to do with linux.
Which is not to say that it might not find it's way into the Ubuntu Desktop mainline patchset, for example. Sure it might not make sense for the mainline kernel, but it surely makes sense for a user focused distro like Ubuntu - they already have patched base and server kernels, so why not a genuine desktop targeted kernel?
Forget thrust, drag, lift and weight. Airplanes fly because of money.
I wonder what BeOS had, that was so good. I mean, was it a scheduler thing? Or was it the pervasive multithreadedness that the OS almost forced upon the developers? Whatever it is, it worked like black magic: BeOS would always listen to the user input, no matter what the heck it was doing in the background, no matter what insane load was on the CPU - your mouseclicks were always reacted upon immediately, your drags were always reacted upon immediately, your typing, resizing, brushstrokes, midi-signals, whatever, always, under any circumstance, were immediately and smoothly followed by the correct response.
I was hoping Windows 2000 would achieve that, then I was hoping Windows XP would achieve that, then I was hoping some of the newer 2.6 kernels in Linux coupled with innovations in X would achieve that - but I was always deeply, utterly disappointed. Then I kinda hoped Vista would get somewhat close to what BeOS did. Oh yeah, now that was a hope decisively smashed.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
I think that's only going to be a good thing, because IMO the arguments against pluggable schedulers are weak. "we need the few people working on this to just make the core better for ALL CASES" is about the most valid i've heard, but linux is too broadly applied to force it to meet all cases. realtime, embedded, servers, desktop: i just don't think one scheduler can be shoehorned to maximize performance for all those. You wind up with a crippled scheduler that really only achieves maximum performance in at most one of those four domains. And the question of there being enough developer minds working on it? you can bet that more commercial enterprise will start throwing money at it when they can customize it for their domain.
It's like the dynamic syscall argument in a way. without dynamic syscalls, the argument goes, all the 'fringe functionality' people have to think harder and have to integrate their stuff into the current syscalls/drivers/subsystems. (apologies ingo) however, without dynamic syscalls, all the "middle of the road" functionality people like hardware manufacturers, are unwilling to release drivers that they essentially have to ask customers to compile as a supported option.
Both, IMO are cases of cutting off your leg to spite your foot.
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CFS can't even cope with a CPU-bound application.
Who here runs Linux on anything with more than 16 cores? Why should everyone else get the shitty end of the stick just because of maybe a dozen institutes with deep pockets?
I think anyone who cares and knows anything about this debate is hoping Linus sees the light and allows work to begin on pluggable schedulers. There are no definitive arguments against having pluggable schedulers, and plenty of formidable ones for them. I never really understood Linus' handling of Con in the past, I really hope that, this time round, the new BFS is given a fair assessment, and if it's found to be better under desktop use patterns, adopted for use in desktop distros.
The idea that the Nokia N900 smartphone uses the same process scheduler as my now-dated laptop as well as my 8 core server is just silly.
I hate printers.
The whole point is moot. Relying on a single maintainer is just plain stupid. "All things being equal" they should choose the code which OTHER people can maintain easier.
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Having read flames from both Theo and Linus, it's difficult to make a fair comparison. Linus is a bit more gentle than Theo, but he is much more likely to be wrong when he flames someone. Neither of them is any good at admitting when they are wrong, but Linus has had a lot more practice at being wrong and not admitting it.
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I guess you didn't read TFA:
In the meantime if you care about CPU utilization and latency then use this. Tomorrow will take care of itself. It's not like if you buy one computer or graphics card, or build one kernel, that you're tied to it for the rest of your life. You use this year what's available and update when the situation warrants it.
No normal user cares about their video encoding being 2 seconds slower (over a 3 hour process) because they wanted to answer their email. If that's really important to you, you are probably doing your video encode overnight or during some time when nobody's using the computer, anyway, and then it doesn't matter.
Instant response is *always*, *always* more important than all other tasks. Always. One of the many, many things BeOS got right.
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