Linux 5.6 is the most exciting kernel in years

https://www.phoronix.com/scan.php?page=article&item=linux-56-features&num=1

by alexellisuk • 6 years ago

714 238 6 years ago

I'm really excited about the NFS client cache stuff.

It's crazy that the whole system grinds to a near halt if it loses connection to the NFS server, from an end user perspective.

I look forward to some time in the future when Debian incorporates this kernel. I prefer to use stock kernels. I used to enjoy messing with my distros, but these days I prefer stability.

LeoPanthera2• 6 years ago

I’m not an NFS expert, and I’ve often wondered about client caching of NFS to improve performance. Does this exist at all currently?

lazyier• 6 years ago

NFS has had caching modes since the beginning. Or at least as long as I have been using it. It's behavior can be controlled by using async or sync options.

NFSv4 is actually quite nice. Anything earlier should be avoided.

bonoboTP• 6 years ago

Sure, the kernel caches everything in RAM by default (as with any other file system, not just NFS).

If you also want to cache on local disk, there's "cachefilesd", which does exactly that. You can specify a certain percentage of the disk that should be kept empty, and cachefilesd will use the rest of the available space for caching.

(It works very well, but is broken on kernel 5.x for me (it just doesn't read from the local cache, even though everything looks fine). But I just mention it off-hand, I don't have time to diagnose this in more detail, I just remain on 4.15 for the time being.)

candiddevmike• 6 years ago

You will be able to use this via buster-backports:

https://backports.debian.org

tracker14• 6 years ago

I've always had better luck with CIFS/SMB myself... but my exposure is relatively limited.

beagle3• 6 years ago

It's crazy that the whole system grinds to a near halt if it loses connection to the NFS server, from an end user perspective.

Indeed. The only solution that works consistently, if the NFS server is not coming back up anytime soon: Enable an NFS server on localhost; add the address of failed NFS server to a local adapter; wait for retry to finally get an error answer; kill ip address and local NFS server.

Client side caching will only delay the inevitable.

nrclark2• 6 years ago

It's great to see all these new features entering the kernel. Here are a couple of other things I've seen in recent changelogs:

- The 5.4 kernel can use CIFS as a root filesystem, meaning CIFS can replace NFS for diskless boot.

- The 5.3 and 5.4 kernels both include prep for merging PREEMPT_RT into mainline. This will be a fantastic addition that benefits embedded Linux nerds like me.

lucb1e• 6 years ago

For more info on the second point: https://en.wikipedia.org/wiki/Linux_kernel#Preemption seems to have something to do with real-time operating systems, but I didn't dive into it.

Edit: Thanks for the downvotes without commenting what I should do differently next time?

zozbot2343• 6 years ago

Having preemption throughout the whole kernel helps with everything Low-Latency whether on desktop, mobile or server systems; it's not limited to the traditional real-time use case, although it might obviously help there as well to some extent.

hactually• 6 years ago

It aims to turn Linux into a real-time OS. The preempty patchset aims to give faster response times but the main focus is to remove all unbounded latencies - for example, situations where the delay can vary depending on other factors.

ronjouch2• 6 years ago

About PREEMPT_RT merge prep: are we talking about the patchset that leads to ultra-low-latency audio-friendly kernels tagged -rt, like https://aur.archlinux.org/packages/linux-rt/ or https://aur.archlinux.org/packages/linux-rt-bfq/ ? If so, I use these for pro audio (for live dsp / effects under 5ms), and have a few questions:

- Will these kernels become obsolete/unnecessary with the merge?

- What about BFQ, is it going to be merged at the same time too?

- This patchset has been existing for a long time. What prevented an earlier merge?

- Is the merge already scheduled to happen for a specific kernel release, or "when it's ready"?

_arvin• 6 years ago

It's essentially just applying these patches: https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt...

The above is for kernel 5.4, as the patchset for 5.5 doesn't exist at the time of this post.

After applying the patches, you'll want to run "make nconfig" or "make menuconfig" and search for CONFIG_PREEMPT_RT and enable it and you should be good to go. The only downside in my experience is Virtual Box doesn't work with the -rt kernel as of right now, so I can't use it as my daily driver. It is a my preferred kernel though for gaming and overall desktop use. I use a custom low-latency kernel when I'm not using the -rt and it's been working well for me.

infinity02• 6 years ago

Random feedbackless downvoting is more and more being clearly abused to censor seemingly random and perfectly acceptable comments. The fact that talking about it is against the site guidelines only makes the problem worse. HN needs to deal with this.

PG seems to understand that a community censorship mechanism needs safeguards. From http://www.paulgraham.com/hackernews.html :

I think it's important that a site that kills submissions provide a way for users to see what got killed if they want to. That keeps editors honest, and just as importantly, makes users confident they'd know if the editors stopped being honest. HN users can do this by flipping a switch called showdead in their profile.

How can editors be "kept honest" if a bunch of their minions can just downvote users for no reason and any complaining is forbidden?

devit• 6 years ago

Currently the Linux kernel disables preemption inside spinlocks and interrupt handlers, and these code sections are not necessarily carefully written to be short and constant-time, so you can in theory get in a situation where all cores are running spinlock or interrupt handler code from low priority threads for arbitrarily long times, preventing higher priority realtime threads to run (which in practice means that whatever hardware you are controlling will be uncontrolled, and thus your self-driving car, rocket, plane or industrial machine might be destroyed).

The PREEMPT_RT patch solves this by reimplementing all kernel spinlocks as mutexes with priority inheritance that are fully preemptible and all interrupt handlers as preemptable threads.

The result is that if you have a bunch of real-time process/thread that do not make system calls, it's guaranteed that in a bounded amount time the highest priority set will be running.

If you do however make system calls (or even if you cause page faults because you didn't call mlockall() and accessed non-mlocked memory), with the exception of some system calls that provide better guarantees, then you can still have kernel spinlock contention with other threads that may hold the same spinlock for an unbounded amount of time, so the system is more limited than dedicated real-time OSes that are careful about this.

zdw• 6 years ago

I wasn't able to find documentation for using CIFS as / - is there a guide somewhere?

What are the advantages of this as compared with NFS?

pkaye4• 6 years ago

CIFS is I think the protocol used on Windows and SAMBA.

henry_flower• 6 years ago

  https://www.kernel.org/doc/Documentation/filesystems/cifs/cifsroot.txt

nrclark2• 6 years ago

I can only speak from personal experience, so don't take this as true for everybody.

But for me, NFS has always been a colossal pain to use. The server has to run in kernel-space. Shares have to be enumerated in /etc. There are a couple of userspace options, but I've never been able to make them work reliably. Once I do get it working, it hangs all the time for no easy-to-debug reason. Also it needs multiple ports to be open, and it expects UID and GID to be the same on client and server.

CIFS has its problems for sure. But it's been pretty straightforward for me every time I've had to use it. If I was trying to set up a production-line machine to flash Linux-based devices, I'd choose CIFS every time because it's so much less hassle. And now that it's rootfs-capable, I just might be able to do it.

Scramblejams• 6 years ago

Any indication whether this make it into Ubuntu 20.04?

edoceo• 6 years ago

It's gonna be 5.4

pkaye4• 6 years ago

They are staying with 5.4 but will back port WireGuard.

axaxs2• 6 years ago

Yikes, that feels like a mistake. 5.4 has awful issues with intel integrated graphics crashing.

thayne4• 6 years ago

Really? Do you have a source for that? (I'm not doubting you, I just haven't heard anything about that, and would be very happy if this is true).

thayne4• 6 years ago

After ubuntu 20.10 is released 20.04 will probably get a later version of the kernel in the linux-hwe package

gchamonlive7• 6 years ago

any reason for choosing ubuntu over arch for personal computers? Or any rolling release distro for that matter

mehrdadn5• 6 years ago

Python packages don't install on /usr/local on Arch which makes it easy to wreck your installation, many projects and scripts out there only support Ubuntu and not Arch, etc.

And I say this as an Arch fan who would rather avoid Ubuntu...

SmellyGeekBoy• 6 years ago

Ubuntu takes all of about 10 minutes to install a full blown desktop and Just Works™ based on my recent experience. Not to take anything away from the amazing tweakability and customizability of Arch, but the target audience is completely different.

gchamonlive7• 6 years ago

really folks, I know the downvote system is useful, but on a question? I mean, I have to know the answer beforehand so I don't get downvoted? I am really tempted not to use this platform anymore

Zardoz84• 6 years ago

Nothing forbides you of installing 5.6 on Ubuntu 20.04 or other older version.

openthc• 6 years ago

Wireguard!! Woot!

I'll be putting this kernel on all production systems, without testing, on Sunday night while everyone is off.

terinjokes• 6 years ago

What product are you launching tomorrow morning?

mehhh• 6 years ago

InstaVPN, it mines your traffuc and gives you ICO tokens as a reward!

ioquatix• 6 years ago

It's a new blockchain-based analytics database which uses SOAP as the wire protocol.

dijit• 6 years ago

But does it need ODBC?

diegocg• 6 years ago

Phoronix loves clickbait titles. This kernel has not even been released, so if you use it on production, you will have to use the testing versions.

Izkata2• 6 years ago

It's a reference to this: https://news.ycombinator.com/item?id=22284463

faitswulff• 6 years ago

Why not Friday night so that everyone can get three full nights of rest before checking to see if anything's on fire?

StavrosK• 6 years ago

Because Sunday still means they get three full nights of rest before checking to see if anything's on fire.

rowanG077• 6 years ago

Don't be a party pooper. Do it on Friday at 7pm. Just after everyone thinks they have a nice relaxing weekend to look forward to.

m-p-32• 6 years ago

See you on LinkedIn!

cyphar• 6 years ago

For some more information on the various features in this release, check out the 5.6-rc1 LWN[1] article. As usual, that article only covers the first week of the merge window (Corbet is probably writing the second part as we speak).

[1] https://lwn.net/SubscriberLink/810780/ae4429af6a4ba40d/

mrr54• 6 years ago

Why are you posting a SubscriberLink to an LWN article to HN? That's not really the point of the links. They're for sharing in small groups not for giving away paid content to thousands of people.

andrewaylett• 6 years ago

LWN are happy to see them posted: https://news.ycombinator.com/item?id=1966033

megous• 6 years ago

Already compiling... :)

gjsman-1000• 6 years ago

Rc1 was released just 30 minutes ago! I’m compiling away!

3fe9a03ccd14ca52• 6 years ago

Year 2038 work beginning to wrap-up for 32-bit systems

I wonder how many of these vulnerable systems will be upgraded to kernel 5.6?

SlowRobotAhead5• 6 years ago

... I’m struggling to think there was ever a reason to store epoch seconds as signed.

Was there a use case for “we need to pretend to have 65 years worth of system time before 1970?

zzo38computer• 6 years ago

Well, now we should use 64-bit timestamps, and 64-bit timestamps is I think sensible to be signed, since there shouldn't need a reason for unsigned 64-bit timestamps.

3fe9a03ccd14ca52• 6 years ago

“In 30 years from now everything will probably be 512 bit and flying cars, right?”

dredmorbius2• 6 years ago

From a favourite Reddit thread:

- Why in the hell would a date value-- particularly one that's an offset-- be signed?

- - How were you planning on indicating dates prior to 1970-01-01?

- - - What date before 1970? We just all assume those do not exist.

- - - - "Now you've made me feel old." "How old are you?" "Let me put it this way: when I was born, time didn't exist."

https://old.reddit.com/r/programming/comments/2b4kpg/conspir...

The full context is ... kind of fun:

https://old.reddit.com/r/programming/comments/2b4kpg/conspir...

macintux• 6 years ago

I would bet they were more confident someone would want to represent data from the recent past than that someone would still be using their research lab OS in 60 years.

ddevault4• 6 years ago

Drooling over that picture of a dozen AMD EPYCs. Those processors are seriously awesome. The newest sr.ht server, tenshi.sr.ht, was provisioned to run git.sr.ht and has an EPYC 7402 24-core @ 3.35 GHz at its heart. It can compile the Linux kernel x86_64 defconfig from scratch on an NVMe in under 30 seconds. Our main build server is also EPYC, a 7281.

SlowRobotAhead5• 6 years ago

Just bought three Dell 7xxx series with Epyc 7402s. Our IT consultant recommended against AMD in favor of Intel. I didn’t like their reasoning.

Side take... I sized our servers to be adequate with the idea virtual cores won’t be turned on. Just assuming more specter and meltdown discoveries, and while AMD has fairer better it’s not impossible they have their own demons.

Aperocky2• 6 years ago

Curious, what are their reasoning?

IgorPartola• 6 years ago

First time I am seeing sourcehut and it seems cool. Is it basically a git, CI, and mailing list platform? Or is there more to it?

ddevault4• 6 years ago

It's basically that, yes. Also has bug tracking, pastes, and wiki services, and a few more in the works.

https://sourcehut.org

greggyb• 6 years ago

I'm sure Drew can provide a much more cogent answer, but Sourcehut also offers consulting services and sponsors open source developers. I recommend checking out the blog at https://sourcehut.org and seeing what's been going on lately.

anderspitman3• 6 years ago

I highly recommend following Drew's work and blog in general. We don't always agree, but I usually come away smarter.

anderspitman3• 6 years ago

Are you running in a colo? Did you bootstrap with a cloud VPS or have you always been on your own hardware?

ddevault4• 6 years ago

Running in a colo. The legacy services were on a VPS but what you know as SourceHut today was always on owned hardware.

the_duke• 6 years ago

I usually don't mind some on-topic advertising, but this is a little too bold for my taste.

eeZah7Ux• 6 years ago

This is not some large corporate-driven, heavily marketed project. It is real, community FLOSS.

GoblinSlayer• 6 years ago

Software for people not for salesmen, is an exception.

ddevault4• 6 years ago

I seriously like these CPUs, and the context in which I evaluated them is sourcehut. Sorry if this comes across as spam.

topspin• 6 years ago

There are a number of new io_uring opcodes appearing with 5.6 as well: fallocate, openat, close, statx, fadvise, madvise, openat2, non-vectored read/write and send/recv.

filereaper• 6 years ago

Looking forward to multipath TCP.

Anyone tried it out yet, how does it look so far?

londons_explore• 6 years ago

Looks good to me, but the Google guys are trying very hard to move the web over to UDP based HTTP/3 instead of MPTCP.

todd38342• 6 years ago

This sounds like a lot of impressive work. I wonder if there would be any benefit to the Linux kernel adopting more of agile release cycle. This waterfall like release surely has to increase the risk surface.

Perhaps the mindset of web software and operating system kernels don’t overlap enough for this to be reasonable?

todd38342• 6 years ago

Not sure why getting downvoted. Is this an ignorant question? Or maybe just not fans of the word agile? Oh well. Guess I’ll just have to ask someone who contributes the the kernel in person the next time I meet one.

wtallis10• 6 years ago

It's a pretty ignorant question; it could also be taken as flamebait trying to start up an agile vs waterfall argument.

New stable kernel branches are released every 2-3 months after weekly release candidates, with bugfix releases in between new stable branches and a new LTS branch every year or so. If you want anything "more agile" than that for OS kernel development, then you're probably prioritizing agile dogma over the realities of trying to not break the most fundamental component of the operating system.

phh• 6 years ago

Linux development is hardly waterfall development.

Take io_uring. It started with a very small subset of syscalls and they are now adding new ones at every release at every stage.

Take bpf. It was meant for networking, and it is slowly transforming into a brain new kind of OS.

Even before a feature lands in mainlinel, we're far from waterfall. Usually a developer will issue a RFC thread implementing a feature as quick and dirty, but as a basis to discuss, and to have people start to test and tinker with it to see what can be done with it.

rmrfchik• 6 years ago

I've rolled back to 4.19 as 5.x kernels works very bad on my setup. Any IO makes system unresponsive. Box is i7, integrated video, ram 32Gb, SSD 512Gb running debian testing. run "apt update" and mouse stops, music skips. 4.19 runs flawless under any reasonable load on this system.

jjgreen• 6 years ago

I'm seeing the same thing (and have also rolled-back).

collyw3• 6 years ago

My machine won't boot when it tried with a version 5 kernel.

LinuxBender2• 6 years ago

What options do you see in /proc/cmdline when you are on 5.x?

LinuxBender2• 6 years ago

And could you add the output of 'lspci -vv' perhaps on pastebin

pjmlp2• 6 years ago

Intel MPX support is completely removed.

A bit sad about this one, Intel should talk to Oracle, ARM and Cambridge Computer Laboratory on how to implement this kind of feature properly.

jeena2• 6 years ago

It's interesting to see how adding of features correlates with the quality of a software. I haven't had problems with wifi on Linux since 2012 (when I came back to it from OS X after leaving 2006 with huge problems before NetworkManager was introduced, etc.). It was until two or three months ago after a kernel update my laptop started dropping the connection with my 5 Ghz network, only at home. It seems to be a common problem with the Qualcom chip driver which worked nice on this laptop for almost two years.

I like progressiveness a lot and also new features, etc. and I found a workaround (switched off 5Ghz at home), so it's ok and I can always install an older kernel too which is the freedom of free software, I wasn't able to do stuff like that on OS X.

theelous3• 6 years ago

Ah! I should try this!

Arch on a dell xps, fine for two years and now have some issue where network buffer doesn't flush (cursory investigation). Have been fairly sure it's an issue post update. Thanks for the idea :)

jeena2• 6 years ago

Yeah mine is a XPS 13 with Arch on it.

zozbot2343• 6 years ago

Quality regressions are common when running bleeding-edge software, this is why going with something LTS is recommended for actual productive use. Now if average non-enterprise folks could get a proper, LTS version of Windows 10...

tsar9x• 6 years ago

Intel iGPU driver (i915) is broken in 5.4 release, I think there are still big issues with QA.

stefs• 6 years ago

i don't really understand this: "The AMD k10temp driver finally starts reporting voltage/current for Zen CPUs and numerous thermal reporting improvements. This is a big step forward thanks to the community but unfortunate these Zen/Zen2 thermal/power reporting bits have taken so long and there are still some mysteries that remain."

why wouldn't AMD set aside a couple of engineers (or at least one) to make sure their processors are supported here? it's not like this would be a huge drain on their manpower resources and the company itself should have an immense interest in the best possible linux support.

thescriptkiddie2• 6 years ago

Zen CPUs are notoriously broken on Linux and AMD doesn't seem to care. If you ever try to install Linux on a first-get Ryzen box and want an uptime longer than 3 days, you'll want to keep this handy:

https://github.com/qrwteyrutiyoup/ryzen-stabilizator

sq_4• 6 years ago

I’m not sure if I’m some weird exception, but I’ve never had issues running Linux at long uptimes on my R5 1600 box.

tbrock• 6 years ago

Yet everyone on here praises these chips and AMD as the (second?) coming of Christ.

I don’t get it, it seems like there are technical leaps but sloppy execution.

In the end I still trust intel (even with specter/meltdown etc) more than AMD because at least my machine:

a) boots

b) stays up long enough to have me even worry about an attack

all_blue_chucks• 6 years ago

You have to disable a key security feature (ASLR) to have a stable AMD-based linux system??

That should have been treated as an all-hands-on-deck emergency by AMD.

stingraycharles• 6 years ago

Does this also apply to Threadrippers? I have a 1950x and it seems to sometimes suffer from stability issues, and wondering whether it’s related.

purplezooey• 6 years ago

crap there's a USB4 already?

Andrex• 6 years ago

The Year 2038 stuff is cool. Do we have projections for how much unpatched stuff might still be around in 2038 to cause issues? The benefit of getting the fixes merged 18 years ahead of time is so those fixes proliferate, but I have to imagine there's a nonzero amount that won't/can't upgrade... Curious if there's any idea of how big an issue this could be, even if we solved everything today.

JohnFen• 6 years ago

There's certainly a lot in there!

However, there's not much that is of interest to me. Given that, plus the mammoth amount of changes in the kernel, I think that I'll be delaying updating to this kernel for a good, long time. Just in case.

Linux 5.6 is the most exciting kernel in years

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