On Tuesday, January 25, 2022 1:26:39 PM EST Andrew M.A. Cater wrote:
On Tue, Jan 25, 2022 at 06:17:16PM +0100, LinAdmin wrote:
When on 16 Mar 2021 I gave the solution in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=981586
I was told from the omnipotent gurus of Debian that nobody needs 32
Bit and the bug was closed.
After that, everybody requiring 32 Bit went with Ubuntu 20.4 LTS
which is not as stubborn as Debian.
No - not quite. That's not what the bug history says. You will find
that Ubuntu isn't supported on all Pi models, for example, but only on
later models that are ARMv7. In general, people are opting for 64 bit
for Pi 3 and Pi 4 - see also Fedora.
If you actually talk to the people doing the work, you often find the
reasons why - they're not all "omnipotent gurus" and they're generally approachable.
As it stands today, we can't support the Raspberry Pi (at any version)
with an official Debian installer because of the method of booting and
the need for non-free firmware. There's a good port for UEFI - and
that's what Fedora is also using, for example - but the need for
non-free firmware persists.
LinAdmin
On 24.01.22 02:23, gene heskett wrote:
I thought I had some cornered earlier today, but when written to
u-sd
and booted, were arm64.
For low latency reasons when a realtime kernel is installed it must
be
for armhf.
Cheers, Gene Heskett.
?? Why must it be armhf - a Pi 4 is massively faster/more capable than
a Pi 1 ?? Could you explain what difference 32 bitness makes?
Simple Andy, and has been explained many times. The bigger stack frame of
arm64 negatively impacts the IRQ latency, making the response to an IRQ
take several microseconds longer. Running a fully preempt-rt kernel on an
i5 can get that time down to 4 u-secs unless you're running something
that needs the nvidia proprietary video driver, which can tie things up
with the irq's locked out for 3+ milliseconds. That's a full showstopper.
On armhf, on a 2gig rpi4b, a kernel I built,
4.19.71-rt24-v7l+ #1 SMP PREEMPT RT Thu Feb 6 07:09:18 EST 2020 armv7l GNU/Linux,
almost 2 years ago makes about 12 microseconds which is fast enough to
run over half a ton of 75 yo sheldon lathe I rebuilt for cnc control. The Linuxcnc latency-test won't even run on an arm64 because the realtime irq capability isn't there, and when measured by other means can be 100 microseconds worse. That's valuable time lost that will manifest itself
in machine crashes that break expensive tooling. Even the half your
little fingernail sized carbide chips that tip our cutting tools cost $20
or more a copy if we buy the better stuff.
The guys that inhabit the linux-rt list are putting a lot of what they've learned back into the regular linux kernel, with the future target being capable of doing this reatime work, but its not all done yet. And its a
heck of a lot faster now than it was at 2.2 because of this, despite the
line count being multiplied by 4 or more since then.
It is Linus's stated target that this happens.
But there is a lot of work yet to be done too, lots of legacy code that
needs re-written to take advantage of what has been learned.
We are the folks who if we want music while we work, will find a radio
and turn it on. Its a different environment for sure but in the long
view it will come together.
We are the unreasonable people G. B. Shaw wrote about when he said all
progress is made by unreasonable people, reasonable folks adapt to the
status quo and get on with it even when things are not optimal.
All the very best, as ever,
To you too Andy, take care and stay well, all of you reading this to see
what trash talk Gene is spewing today.
Andy Cater
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <
http://geneslinuxbox.net:6309/gene>
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