riscv64 is now an official Debian architecture (rebootstrap in progress)

https://lists.debian.org/debian-riscv/2023/07/msg00053.html

by pabs3 • 3 years ago

135 49 3 years ago

lists.debian.org

stevefan1999• 3 years ago

What about SIMD support? Most software (like ffmpeg) clearly aren't having nor is going to use the current SIMD specification for rv64

photonbeam2• 3 years ago

riscv provides a vector unit instead of a traditional simd

cbm-vic-20• 3 years ago

I thought I had read somewhere that the Packed SIMD (P) extension was still going to be developed for implementations that don't need the full-blown Vector (V) extension, for example, embedded processors for digital signal processing.

https://github.com/riscv/riscv-p-spec/ https://github.com/riscv/riscv-v-spec/

dzaima2• 3 years ago

rvv1.0 is frozen, and ffmpeg does contain some usage of it: https://git.ffmpeg.org/gitweb/ffmpeg.git/tree/HEAD:/libavcod...

arp242• 3 years ago

To contextualize this – because I had no idea if those 13 files constituted "a lot", "very little", or anything in between – here's a comparison of amount of asm code for each platform:

           Files        Lines      Blanks    Comments       Code
  aarch64     35       24,703       1,999           0     22,704
  alpha        3          471          57           0        414
  arm         69       30,600       1,975           0     28,625
  loongarch    6        6,531         485           0      6,046
  ppc          2          605          50           0        555
  riscv       13        1,284          71           0      1,213
  x86         97       48,669       4,260        4418     39,991

This is a very rough comparison and doesn't take in to account the C code for every platform (which seems to scale roughly but not exactly the same), programming style, architecture differences, etc. but it should be roughly accurate.

leonheld• 3 years ago

This is the real issue with adopting new architectures, imho. So many packages claim to support arm, for example, whilst not enabling the proper optimisation flags, rendering it unusable. A loooot of work we take for granted has been put to optimize things for x86.

camel-cdr3• 3 years ago

The packed simd extension isn't ratified and mostly aimed at embedded processors that need to do digital signal processing.

The vector extension (rvv) is what's important for desktop and server chips, and it is already ratified.

ffmpeg for example already has some things ported to rvv [0], and many projects are already working on support.

The problem is that there currently isn't any consumer hardware that supports the ratified vector extension. Sipeed announced [1] that they are working on a RVA22+V soc based on the C908 chip, this will likely be the first one developers can get their hands on.

[0] https://git.ffmpeg.org/gitweb/ffmpeg.git/tree/HEAD:/libavcod...

[1] https://twitter.com/SipeedIO/status/1654055669774036993

tsukikage• 3 years ago

ToT llvm autovectorisation for riscv "V" 1.0 is actually really rather decent. Not as good as handcoding, natch, but can get to within a factor of two or better especially on workloads which are mostly simple tiny loops over data that's contiguous or has constant stride, as in h264 encoding.

Of course, the question is somewhat moot until we have development hardware available to buy that supports the ratified 1.0 version of the vector extensions. So, another year or so I'd guess.

kosolam• 3 years ago

Sounds exciting. I haven’t figured yet how I can make use of riscv but my hands are scratching and I’m an avid debian user. Anyone here does interesting hobby projects with riscv hardware?

jeffbee2• 3 years ago

It's interesting that the project officially supports riscv64 but other architectures in a similar ecosystem niche, but vastly larger installed base, like SH4, have been unofficial ports for decades. Perhaps this is a good comparative example of how to effectively engage the community, or fail to.

orra• 3 years ago

I can't speak for why SH4 was always unofficial, but from a vibes perspective today, RISC-V feels like an architecture on the up. That probably helps attract more developers, and ultimately it takes people to do the work.

ncts• 3 years ago

Number of active maintainers is a key factor. Compare to this: https://lists.debian.org/debian-mips/2023/07/msg00012.html

lambda3• 3 years ago

Where are you getting the "vastly larger installed base"? On popcon riscv64 is a lot higher than sh4: https://popcon.debian.org/stat/submission-1year.png

There may be more hardware out there with SH4 processors, like some NAS boxes, but are they using or contributing to Debian? And when I look at a list of hardware with SuperH processors, half of the links are broken links: https://elinux.org/Processors#SuperH

SuperH seems like a niche architecture mostly supported by a single vendor and available in a few devices mostly in the Japanese market, without a huge amount of use in the Debian community.

RISC-V may not yet have as much extant hardware available, but there's tons of active development, and the open licensing model means that a lot of companies are working on RISC-V chips, which will then flow into hardware.

jeffbee2• 3 years ago

I'm not suggesting that SuperH would become an official port today when it is clearly dead. But the question is why it was never an official port even when it was in its prime. As for the installed base, it is absolutely terrifyingly large. They had a lot of wins in automotive, and popular consumer products like Sonos are based on it, or were for the first decade of that product line, and those products also run Linux.

beebmam• 3 years ago

Where would I go about buying a serious risc-v PC? So far, all I've seen are either tiny devices without much computation power, or emulation support.

Is risc-v a legitimate platform for serious computation or is it targeted at embedded devices?

saagarjha• 3 years ago

There are people working to make server-level chips for it but none of them are really quite ready yet.

snvzz6• 3 years ago

Ventana Veyron is due before year end.

Tenstorrent Ascalon (led by who was Apple M1 lead architect) promises competitive performance with projected AMD Zen5, and is due 2024 (same as Zen5).

panick21_2• 3 years ago

RISC-V by design and be ambition is for everything, serious compute and embedded. Its just that its far easier to release embedded chips and that standard for that was ready far earlier.

Serious compute simply takes far longer in terms of product cycle and the relevant standard came far later.

A lot of use for RISC-V is also not in places that is target at end consumer devices.

There is not much yet in terms of RISC-V PC? The HiFive Pro P550 should be coming out at some point. Or the Unmatched currently.

https://www.sifive.com/boards/hifive-unmatched

https://www.sifive.com/boards/hifive-pro-p550

Companies working on high performance RISC-V are: Esperanto, SiFive, Ventana Micro Systems and Tenstorrent.

snvzz6• 3 years ago

And Rivos.

httgp• 3 years ago

Noob question - are they somehow better at AI/ML workloads than regular x86_64?

camel-cdr3• 3 years ago

https://milkv.io/pioneer seems to be what you are looking for, but I'd only recommend it for developers who are working on getting things like gpu drivers ported.

For most development smaller SBCs are enough, and I'd recommend waiting for RVA22/23 profile supporting hardware before spending a lot of money, because most current chips use the non standard vector isa and don't support all profile extensions, because they where created before everything was ratified.

rwmj3• 3 years ago

At least 4 companies are working on server-class chips, targeting "Xeon-like" performance. Of course without actual hardware to test you should take those claims with a grain of salt for the moment.

If you want a cheap, low-end single board computer you can use right now, then I'd go for either the Vision Five 2 or the Sipeed Lichee Pi 4A. Performance won't be that great, but it'll run Fedora, Debian, Ubuntu or Yocto distros pretty much out of the box. I'm working on a Hifive Unmatched vs VF2 vs Sipeed vs Raspberry Pi 4B performance comparison right now, which will appear on https://rwmj.wordpress.com

IshKebab• 3 years ago

I think there are a few reasons why there's no point currently:

* There aren't really any available for a reasonable price.

* A lot of the desktop related stuff is still in the process of being specified and ratified. If you buy something now it will probably use a load of ad-hoc features especially for booting.

* It doesn't really make any difference to running software, unless you are writing assembly. If you just want to play around with RISC-V assembly an emulator or cheap embedded hardware is a lot better option.

snvzz6• 3 years ago

If you want to play with running Linux on RISC-V today or doing any porting work, VisionFive2 is where it's at.

They are serious about upstream support[0].

0. https://rvspace.org/en/project/JH7110_Upstream_Plan

zX41ZdbW2• 3 years ago

We have recently added official builds of ClickHouse for RISCV-64: https://github.com/ClickHouse/ClickHouse/pull/31398

Although the support existed for several years, it was not automated until recently.

pabs34• 3 years ago

What build hardware are you using for riscv64?

zX41ZdbW2• 3 years ago

We are doing cross-compilation, and all the targets can be built on x86_64 or aarch64 servers or laptops/desktops; in the CI, we are using x86_64 machines in AWS.

rwmj3• 3 years ago

Why are they "rebootstapping"? Or does that mean they're just recompiling all the .debs again, but using the existing environment? (For context I've bootstrapped Fedora on riscv64 from scratch three times, and I wouldn't be keen to ever have to do it again.)

dima55• 3 years ago

"rebootstrap" is the tool used today to bring up a new architecture. My understanding is that most of the process is now automated.

pabs34• 3 years ago

The rebootstrap being referred to here is not Helmut's automated rebootstrap tool, but about the fairly manual process of rebuilding an existing unofficial port as on official port, the steps for this are on the new port docs wiki page:

https://wiki.debian.org/PortsDocs/New#Official_port

snvzz6• 3 years ago

Debian unofficial ports are built separately.

As RISC-V is now official, it needs to be rebuilt with the infrastructure that builds all official architectures.

There should be no issues, as the unofficial port is already building over 95% of the Debian package library. Note that Debian is the biggest distribution, so this is no small feat.

In a couple weeks, it should all be sorted, with the official port built to the same level the unofficial port was.

rwmj3• 3 years ago

Sure, we also build most of Fedora on a separate build system (http://fedora.riscv.rocks/koji/) so it's a pretty similar situation.

pabs34• 3 years ago

The rebootstrap is done because unofficial ports build servers usually are not owned or run by the Debian project, but by the porting teams themselves, who could be and often are random people who are not yet Debian members. So we don't necessarily want to use all of those .debs because they might not be rebuildable, or they might have artefacts from whatever hacky bootstrap process the first build used. The bootstrap process is a QA strategy to have more trust in the resulting binary packages.

Longer term we want all new ports to be cross-built from an existing architecture, but we don't have cross-buildds yet. The rebootstrap tool is a work-in-progress QA tool for making cross-building bootstrap for new arches a viable strategy.

https://wiki.debian.org/HelmutGrohne/rebootstrap https://wiki.debian.org/DebianBootstrap https://crossqa.debian.net/ https://wiki.debian.org/PortsDocs/New

Even longer term, we should do a bootstrap of all architectures from scratch using the approach of Guix, Bootstrappable Builds and Reproducible Builds; start with ~500 bytes of hand-written machine code plus all the source code and build enough to get a build server up, then go from there.

https://bootstrappable.org/ https://reproducible-builds.org/ https://www.aikidev.net/~vagrant/talks/2023/fossy/Breaking_t...

riscv64 is now an official Debian architecture (rebootstrap in progress)

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