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Re: RedSleeve Linux on Raspberry Pi

Posted: Wed Mar 28, 2012 10:51 am
by gordan
Just in case anybody is interested in a Fedora-like distribution but a little less bleeding edge and with the goal posts a little more static, you may want to take this for a spin:

http://www.redsleeve.org/

As is the case with CentOS and Scientific Linux, mention of the upstream vendor is disallowed, but if you are familiar with those two, you can probably guess what RedSleeve is based on.

So, please take it for a spin, and report success/failure/bugs/patches on the mailing list.

Re: RedSleeve Linux on Raspberry Pi

Posted: Mon Apr 09, 2012 2:32 pm
by Montala
Does this mean that we will soon start to see versions developed specifically for the Raspberry Pi?

Re: RedSleeve Linux on Raspberry Pi

Posted: Mon Apr 09, 2012 2:39 pm
by jamesh
Technically, all the distributions that say they are for Raspi, are actually developed specifically for the Raspi. Not the kernel etc (that always standard), but the ancillary bits needed to deal with the Raspi specific hardware etc. That was makes it a 'distribution', rather than just Linux. So, if the kernel version is the same on two different Raspi distributions, then under the skin they are the same (usually). It's all the bit around the kernel that make the differences in distributions - drivers, libraries etc.

Although having reread the previous post, I'm not sure I've answered the right question!

Re: RedSleeve Linux on Raspberry Pi

Posted: Mon Apr 09, 2012 3:05 pm
by Montala
Thanks James… well you sort of have!

I do understand that at present anyone with a desktop PC, or laptop/netbook currently has a choice of a very large number of Linux "derivatives" and I also accept that, as you say, although the kernel may be common, many other "bits" have to be added (or changed) before any of them will actually be compatible with the specific Raspberry Pi hardware, which uses a different "CPU" for a start. Then of course there is a choice of different desktops, web browsers, file handling systems etc. to suit the preferences, or requirements, of the individual user.

Currently we have Debian and Fedora already available, and it doesn"t look as if a "version" of Puppy is too far away either, so my question was really whether we might also see a "distribution" of RedSleeve developed specifically for the Raspberry Pi computer, which is actually mentioned on the website, also made available in due course… yes, I did  take the trouble to check it out first!

I can actually see the Linux "camp" itself receiving a massive boost from the Raspberry Pi, as purchasers realise that there is a "free" alternative to Windows, after all… but that is already being discussed elsewhere!

Re: RedSleeve Linux on Raspberry Pi

Posted: Mon Apr 09, 2012 3:27 pm
by gordan
I sincerely doubt there will ever be a distribution specific to a particular SoC. What would be the point? There might be a handful of packages that are specific to the SoC (e.g. the kernel and video codec libraries), but there is absolutely no reason for everything else to be anything other than generic.

RedSleeve is a generic distribution and will work on any ARMv5 or newer SoC. R-Pi is ARMv6 so it will work fine.

Re: RedSleeve Linux on Raspberry Pi

Posted: Mon Apr 09, 2012 5:59 pm
by jojopi
gordan said:

RedSleeve is a generic distribution and will work on any ARMv5 or newer SoC. R-Pi is ARMv6 so it will work fine.
Except that all(?) ARMv5 distributions are compiled with software floating point, so the performance can be an order of magnitude worse than the Pi is capable of.

Most distros have an ARMv7 port with hardware FP, but that will not run on a Pi at all.

Taking into account that the Pi is likely to outsell many other ARM development boards combined, I think there is a very good case for a full ARMv6+VFP port of some distro to be built.

Further generic ARMv5 ports would then be very unattractive.

Re: RedSleeve Linux on Raspberry Pi

Posted: Tue Apr 10, 2012 10:32 am
by gordan
Actually, the floating point issue isn't anywhere nearly as clear cut as you are implying. There are three FP options on ARM:

1) soft - fully emulated

2) softfp - hardware FPU is present and FPU values get passed in integer registers then copied over to FPU registers. The problem is that each register copy causes a pipeline stall.

This has noticable performance implications in that a lot of time is spent in function prologue and epilogue copying data back and forth to FPU registers. This could be 20 cycles or more. In a lot of cases that means that softfp will actually be slower than fully emulated FP. soft and softfp can be intermixed (same ABI).

3) hardfp - full hardware FP with direct FP register passing. ABI incompatible with soft/softfp

This is why no distribution has bothered with anything between armv5tel (soft) and armv7hl (hardfp) - there is just not enough gain in softfp.

Re: RedSleeve Linux on Raspberry Pi

Posted: Tue Apr 10, 2012 10:53 am
by jamesh
softfp did provide noticeable improvements running linpack on Raspi I think. But it does depend on the use case.

Re: RedSleeve Linux on Raspberry Pi

Posted: Tue Apr 10, 2012 11:15 am
by jojopi
gordan said:

This is why no distribution has bothered with anything between armv5tel (soft) and armv7hl (hardfp) - there is just not enough gain in softfp.
That might explain why you have not bothered with softfp or mixed soft/softfp, but it does not explain the lack of armv6hl.  It can only be that you think armv6 boards with vfp are not important enough.

Re: RedSleeve Linux on Raspberry Pi

Posted: Tue Apr 10, 2012 12:01 pm
by gordan
There are two points to consider here.

1) To some extent you are right about the importance of armv6hl - there are so few ARMv6+VFP SoCs (VFP is optional rather than mandatory on ARMv6) in non-embedded products that it hasn't justified the amount of work required for any distribution I am aware of to target armv6hl.

2) There is also the much bigger issue of toolchains - RedSleeve is based on a certain upstream distribution which sets the toolchain used. It is only relatively recently that the toolchains began supporting hardfp sufficiently well to enable building the entire distro. As and when the upstream distro is based on the toolchain sufficiently new to allow for a full hardfp build, I will make it.

2.1) Since hardly anybody builds for the armv6hl target (as opposed to armv7hl), the code paths aren't all that thoroughly explored so the incidence of various toolchain related bugs is likely to be considerably higher than for armv7hl.

Re: RedSleeve Linux on Raspberry Pi

Posted: Fri Jun 01, 2012 8:13 am
by fireshipjohn
I've got a version running on the Pi - looks very promising.

Details are here http://opensource.wrenhill.com/?p=123

I've Included a downloadable image to get started.