Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 18:46, Stefan Monnier wrote:

There I disagree, Greg, it makes a handy download tool, directly
from wherever, directly to the machine that needs it.  That,
apt/synaptic and git are the major net tools I use.  Obviously I'm
not trying to run them simultaneously. Every machine here 7 ATM, can
browse the net, making it very easy to keep them up to date.

Do you have some big honking KVM to multiplex all those machines
onto your screen and keyboard, or do you actually have 7 screens and
7 keyboards and you need to walk over from one to the other?

Here I was going to ask if you'd ever hear of ssh and sshfs. but thn I read
the next paragraph.


Then why do you need to run firefox on the rpi's?  I'd use Firefox on my
desktop and if I need to download files to one of the other machines,
I'd copy those files via `scp` or `sshfs` or even NFS (NFS
authentication is a PITA in my experience, but if you can use
a dedicated local network where you all machines can somewhat trust
each other, NFS can be a good option).


NFS is a pita.
sshfs just works for file movement. ssh -X for login stuff. It helps of 
course that I am the only "live user"



And Odroid?  Where do I send condolence flowers?


I was not super happy with some aspects (e.g. the fact that I can't get
the source code for some of the firmware, including the Petitboot that's
included, nor is there any way to change that firmware's config (e.g. to
make Petitboot use the serial console rather than the HDMI output)), but
in practice it works well and the hardware is fully supported by the
vanilla Linux kernel.

It wasn't anywhere near primetime ready when I bought on 7 or 8 years 
ago. Actually supporting linux was not then a prioirty. I use winderz 
stuff for target practice here.


 Stefan

.


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 

Re: swap-fle on arm64, need to disable, how?

[Max Nikulin]

On 02/10/2023 03:01, hw wrote:

Once you figured
it out, you add sufficent amounts of RAM and use zram.


Is it possible for *Pi boards? Even laptops may have soldered RAM with 
no spare slots.


ZRAM may be fast, but if you need, say +2G in comparison to physical RAM 
size, the chance of success is fair in the case of RAM size of 16G. If a 
board has just 2G of RAM then you need to be really lucky to get extra 
2G by compression.


Perhaps Gene's setup is no optimal, but swap on SSD, despite its 
disadvantages, may be an alternative to using a more performant board 
for building of applications.

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 16:01, hw wrote:

On Sun, 2023-10-01 at 04:31 -0400, gene heskett wrote:

On 9/30/23 23:22, hw wrote:

On Sat, 2023-09-30 at 18:29 -0400, gene heskett wrote:

On 9/30/23 13:28, Matthias Böttcher wrote:

sudo dphys-swapfile swapoff
sudo systemctl stop dphys-swapfile.service
sudo systemctl disable dphys-swapfile.service

.

However that did give me a clue about getting rid of zram0, which has
been done now, thank you. Now I hope to uncomment the SSD line in fstab.


Well, zram is the way to go; why would you still use swap partitions
or swap files instead?  Are you deliberately trying to wear out your
SSDs or to slow down your computer?


zram is probably the way to go for board with lots of dram. Something
the pi's don't have.


You only need as much RAM as is sufficient for what you're doing.
That's the way to go while having more RAM doesn't hurt much.

Swapping to SSDs is slow.  If it's faster than zram, something must be
wrong.

In an earlier message you're saying RAM isn't an issue.  So why are
you messing with it?

10GB swap on an SSD you're actually tring to use?  Ugh ...  It's maybe
ok for preventing the system from going into some undefined and
undesirable state from running out of memory for instances in which
you're trying to figure out how much RAM you need.  Once you figured
it out, you add sufficent amounts of RAM and use zram.

BTW, how do you prevent breaking the lathe when the pi or the software
fails?  There's things that can go wrong and lathes tend to be rather
powerful tools.  Do you have some device to detect failures and some
kind of break that stops the lathe immediately when something goes
wrong?



There are several checks which can stop lcnc in the next millisecond. 
They have been well tested, but have yet to do so while working. I am 
slowly converting all my stepper drivers to closed loop versions, the 
next generation in motors, which have several advantages over std 
steppers. First they control motor power with the magnitude of the 
error, so motors don't run burn your hand hot unless being really 
pushed. 2nd, they get to where lcnc ends them or if they can't get 
there, they'll kill the motor power and advise lcnc of the failure which 
if wired correctly, shuts lcnc down in its tracks a millisecond later. I 
now have 5 of those motors turning things and that failure has yet to 
occur while working.  I guess I'm sold.


Take care & stay well, hm

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 

Re: swap-fle on arm64, need to disable, how?

[Stefan Monnier]

>>> There I disagree, Greg, it makes a handy download tool, directly
>>> from wherever, directly to the machine that needs it.  That,
>>> apt/synaptic and git are the major net tools I use.  Obviously I'm
>>> not trying to run them simultaneously. Every machine here 7 ATM, can
>>> browse the net, making it very easy to keep them up to date.
>> Do you have some big honking KVM to multiplex all those machines
>> onto your screen and keyboard, or do you actually have 7 screens and
>> 7 keyboards and you need to walk over from one to the other?
> Here I was going to ask if you'd ever hear of ssh and sshfs. but thn I read
> the next paragraph.

Then why do you need to run firefox on the rpi's?  I'd use Firefox on my
desktop and if I need to download files to one of the other machines,
I'd copy those files via `scp` or `sshfs` or even NFS (NFS
authentication is a PITA in my experience, but if you can use
a dedicated local network where you all machines can somewhat trust
each other, NFS can be a good option).

> And Odroid?  Where do I send condolence flowers?

I was not super happy with some aspects (e.g. the fact that I can't get
the source code for some of the firmware, including the Petitboot that's
included, nor is there any way to change that firmware's config (e.g. to
make Petitboot use the serial console rather than the HDMI output)), but
in practice it works well and the hardware is fully supported by the
vanilla Linux kernel.


Stefan

Re: swap-fle on arm64, need to disable, how?

[hw]

On Sun, 2023-10-01 at 04:31 -0400, gene heskett wrote:
> On 9/30/23 23:22, hw wrote:
> > On Sat, 2023-09-30 at 18:29 -0400, gene heskett wrote:
> > > On 9/30/23 13:28, Matthias Böttcher wrote:
> > > > sudo dphys-swapfile swapoff
> > > > sudo systemctl stop dphys-swapfile.service
> > > > sudo systemctl disable dphys-swapfile.service
> > > > 
> > > > .
> > > However that did give me a clue about getting rid of zram0, which has
> > > been done now, thank you. Now I hope to uncomment the SSD line in fstab.
> > 
> > Well, zram is the way to go; why would you still use swap partitions
> > or swap files instead?  Are you deliberately trying to wear out your
> > SSDs or to slow down your computer?
> > 
> zram is probably the way to go for board with lots of dram. Something 
> the pi's don't have.

You only need as much RAM as is sufficient for what you're doing.
That's the way to go while having more RAM doesn't hurt much.

Swapping to SSDs is slow.  If it's faster than zram, something must be
wrong.

In an earlier message you're saying RAM isn't an issue.  So why are
you messing with it?

10GB swap on an SSD you're actually tring to use?  Ugh ...  It's maybe
ok for preventing the system from going into some undefined and
undesirable state from running out of memory for instances in which
you're trying to figure out how much RAM you need.  Once you figured
it out, you add sufficent amounts of RAM and use zram.

BTW, how do you prevent breaking the lathe when the pi or the software
fails?  There's things that can go wrong and lathes tend to be rather
powerful tools.  Do you have some device to detect failures and some
kind of break that stops the lathe immediately when something goes
wrong?

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 14:06, Stefan Monnier wrote:

There I disagree, Greg, it makes a handy download tool, directly from
wherever, directly to the machine that needs it.  That, apt/synaptic and git
are the major net tools I use.  Obviously I'm not trying to run them
simultaneously. Every machine here 7 ATM, can browse the net, making it very
easy to keep them up to date.


Do you have some big honking KVM to multiplex all those machines
onto your screen and keyboard, or do you actually have 7 screens and
7 keyboards and you need to walk over from one to the other?

Here I was going to ask if you'd ever hear of ssh and sshfs. but thn I 
read the next paragraph.



Personally, I think I'd do neither: I'd have all those little buggers
headless and control them exclusively remotely via SSH (there could be
some alternatives like remote desktop or web-server UIs, but I find the
command line just a lot more convenient).
[ That's what I do with my BananaPi and my Odroid servers.  ]


And Odroid?  Where do I send condolence flowers? I spent several days 
trying to install a linux on it. Wound up bricking it. That outfit is 
married to uefi and our socalled shim was nowhere near ready for prime 
time. They said I'd need to get about $275 in jtag tools to unbrick it. 
When I took my problem with that back I was told our way or or the 
hiway. So I ordered a rpi3b and did the job with it.  They will never 
see another penny from me. That is their problem, I use what works, and 
theirs didn't.




 Stefan

.


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 

Re: swap-fle on arm64, need to disable, how?

[Stefan Monnier]

> There I disagree, Greg, it makes a handy download tool, directly from
> wherever, directly to the machine that needs it.  That, apt/synaptic and git
> are the major net tools I use.  Obviously I'm not trying to run them
> simultaneously. Every machine here 7 ATM, can browse the net, making it very
> easy to keep them up to date.

Do you have some big honking KVM to multiplex all those machines
onto your screen and keyboard, or do you actually have 7 screens and
7 keyboards and you need to walk over from one to the other?

Personally, I think I'd do neither: I'd have all those little buggers
headless and control them exclusively remotely via SSH (there could be
some alternatives like remote desktop or web-server UIs, but I find the
command line just a lot more convenient).
[ That's what I do with my BananaPi and my Odroid servers.  ]


Stefan

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 11:01, Curt wrote:

On 2023-10-01, gene heskett  wrote:



Andy, with good luck, you may make to your 89th birthday, which with
good luck I'll celebrate next Wednesday.  I certainly hope you do. By
then you will not see any humor in trying to remember what, if anything,
you had for breakfast this morning. I seem to have reached that point.
And I'm not any happier for it either.


What are you building? A space ship to get out of here?


That is an inviting thought, but I'll likely die en-route.

I'd show folks what I am building but the server does not like jpegs or 
png's.



Cheers, Gene Heskett.





.


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 

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 09:39, Andrew M.A. Cater wrote:

On Sun, Oct 01, 2023 at 08:58:36AM -0400, Greg Wooledge wrote:

On Sun, Oct 01, 2023 at 05:07:48AM -0400, gene heskett wrote:

You've a good view of this hw. However swap is not important to run
linuxcnc, in fact its to be avoided because it messes with realtime
response. Linuxcnc needs, even with much of the control offloaded to mesa
and similar smart cards, it still needs to check what the machine is doing
1000 times a second. The way I'm doing it, the wobble in this timing as 50
to 80 microseconds, which doesn't bother the machine all that much, the real
time killer is firing up firefox which can lock out the irq response for
hundreds of milliseconds.  So I don't carve metal and browse the web at the
same time.


If Firefox is really just for "browsing the web", and is not part of
the user interface for the CNC pieces, I don't understand why you run
Firefox on this machine at all.  I would run the browser on a separate
computer, one which isn't so critical to your operation.



Echoing Greg:

2G is a fairly small amount of memory - by default the *Debian* install
for RPi 4 now gives you 1G of swap on whatever medium - which you should
never need to use.

It would make sense for something real time critical to be on a 2GB or 4GB RPi
on it's own - if you're running modellers or whatever for 3D printing, that
might be different but a command line or simplest web interface might be
best. You REALLY don't want anything extraneous.

Pi 4GB or 8GB are now available more or less: your BananaPi - you are *very*
much on your own.

All best, sa ever,

Andy
[amaca...@debian.org]

.
The bananapi-m5 at $80 USD is very much the superior pi except for no 
radio, 4 core cpu at 2 GHz, w/o a fan, 4G of dram, 16G of m2 disk 
onboard, and all 4 usb ports are usb3 speed. The armbian install runs on 
ubuntu jammy repos. Got a pile of them here.


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 

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 08:59, Greg Wooledge wrote:

On Sun, Oct 01, 2023 at 05:07:48AM -0400, gene heskett wrote:

You've a good view of this hw. However swap is not important to run
linuxcnc, in fact its to be avoided because it messes with realtime
response. Linuxcnc needs, even with much of the control offloaded to mesa
and similar smart cards, it still needs to check what the machine is doing
1000 times a second. The way I'm doing it, the wobble in this timing as 50
to 80 microseconds, which doesn't bother the machine all that much, the real
time killer is firing up firefox which can lock out the irq response for
hundreds of milliseconds.  So I don't carve metal and browse the web at the
same time.


If Firefox is really just for "browsing the web", and is not part of
the user interface for the CNC pieces, I don't understand why you run
Firefox on this machine at all.  I would run the browser on a separate
computer, one which isn't so critical to your operation.

There I disagree, Greg, it makes a handy download tool, directly from 
wherever, directly to the machine that needs it.  That, apt/synaptic and 
git are the major net tools I use.  Obviously I'm not trying to run them 
simultaneously. Every machine here 7 ATM, can browse the net, making it 
very easy to keep them up to date.

.


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 

Re: swap-fle on arm64, need to disable, how?

[David Wright]

On Sun 01 Oct 2023 at 13:39:17 (+), Andrew M.A. Cater wrote:
> On Sun, Oct 01, 2023 at 08:58:36AM -0400, Greg Wooledge wrote:
> > On Sun, Oct 01, 2023 at 05:07:48AM -0400, gene heskett wrote:
> > > You've a good view of this hw. However swap is not important to run
> > > linuxcnc, in fact its to be avoided because it messes with realtime
> > > response. Linuxcnc needs, even with much of the control offloaded to mesa
> > > and similar smart cards, it still needs to check what the machine is doing
> > > 1000 times a second. The way I'm doing it, the wobble in this timing as 50
> > > to 80 microseconds, which doesn't bother the machine all that much, the 
> > > real
> > > time killer is firing up firefox which can lock out the irq response for
> > > hundreds of milliseconds.  So I don't carve metal and browse the web at 
> > > the
> > > same time.
> > 
> > If Firefox is really just for "browsing the web", and is not part of
> > the user interface for the CNC pieces, I don't understand why you run
> > Firefox on this machine at all.  I would run the browser on a separate
> > computer, one which isn't so critical to your operation.
> >
> Echoing Greg:
> 
> 2G is a fairly small amount of memory - by default the *Debian* install
> for RPi 4 now gives you 1G of swap on whatever medium - which you should
> never need to use.
> 
> It would make sense for something real time critical to be on a 2GB or 4GB RPi
> on it's own - if you're running modellers or whatever for 3D printing, that
> might be different but a command line or simplest web interface might be
> best. You REALLY don't want anything extraneous.
> 
> Pi 4GB or 8GB are now available more or less: your BananaPi - you are *very*
> much on your own.

Back in 2018, Gene's explanation was:

  https://lists.debian.org/debian-user/2018/11/msg00049.html

Cheers,
David.

Re: swap-fle on arm64, need to disable, how?

[David Wright]

On Sun 01 Oct 2023 at 04:31:26 (-0400), gene heskett wrote:
> On 9/30/23 23:22, hw wrote:
> > On Sat, 2023-09-30 at 18:29 -0400, gene heskett wrote:

> > > However that did give me a clue about getting rid of zram0, which has
> > > been done now, thank you. Now I hope to uncomment the SSD line in fstab.
> > 
> > Well, zram is the way to go; why would you still use swap partitions
> > or swap files instead?  Are you deliberately trying to wear out your
> > SSDs or to slow down your computer?
> > 
> zram is probably the way to go for board with lots of dram. Something
> the pi's don't have. My only pi is an early rpi4b, Claims 2G, shows
> 1.8G. I tend to do big things with it.

OTOH the Description says:

 "zram-tools uses this module to set up compressed swap space.
  This is useful on systems with low memory or servers
  running a large amount of services with data that's easily swappable
  but that you may wish to swap back fast without sacrificing disk
  bandwidth.

 "By default it allocates 100MB of RAM, you can configure this in
  /etc/default/zramswap."

> To steal over a gig for zram style swap does not make any sense to me.

Did they just copy a Fedora configuration? I've read that this is what
it does.

> > Fedora has it by default since a while, and at first I thought it's a
> > very stupid idea.  In practise, I can't be bothered anymore to create
> > these annoying swap partitions.  They're only a waste of disc space.
> > There haven't been any issues with it, and when the machine runs out
> > of memory, using swap partitions or swap files isn't going to fix
> > that.
> 
> But with zram  taking over half its memory, its into swap and slowing
> down quicker, and plumb out of memory for big jobs, when it could
> still be working fine with bigger, albeit probably slower than zram,
> swap.

I hadn't come across this package before, so I installed it on an idle
laptop. With configuration completely untouched, OOTB, it reports:

  $ free 
 totalusedfree  shared  buff/cache   
available
  Mem:16256864  197692109996721848 5059500
15714244
  Swap: 262140   0  262140
  $ cat /proc/swaps 
  FilenameTypeSizeUsed
Priority
  /dev/zram0  partition   262140  0   100
  $ 

Cheers,
David.

Re: swap-fle on arm64, need to disable, how?

[Darac Marjal]

On 01/10/2023 09:31, gene heskett wrote:




Fedora has it by default since a while, and at first I thought it's a
very stupid idea.  In practise, I can't be bothered anymore to create
these annoying swap partitions.  They're only a waste of disc space.
There haven't been any issues with it, and when the machine runs out
of memory, using swap partitions or swap files isn't going to fix
that.


But with zram  taking over half its memory, its into swap and slowing 
down quicker, and plumb out of memory for big jobs, when it could 
still be working fine with bigger, albeit probably slower than zram, 
swap.


I've no clue how much the zram compression slows it in terms of thru put.

I wiped out the git clone of linuxcnc by re-arranging that SSD 
yesterday, but I'll do another build later today and see how long it 
takes with real swap.


Thank you. Take care & stay well..

Cheers, Gene Heskett.


I might be wrong, but zram probably wouldn't be so popular if it always 
consumed 100% of the space allocated to it.


Instead, I believe zram works like this:

 * The system sets up a zram RAM disk. This will start by consuming a
   few pages of RAM (plus whatever is required by the driver)
 * As memory pressure increases (i.e. as RAM starts to fill up with
   pages), the system will swap the less frequently used pages to a
   swap device.
 * In the case of zram, this essentially moves a page from one part of
   RAM to a smaller representation in another part of RAM.
 * The zram RAM disk will increase in size, but because of the
   compression, it will expand at a slower rate than the rate of pages
   being moved out of RAM, therefore there is a net gain in free RAM.
 * Similarly, when a page is swapped back from zram to RAM, the RAM
   disk will shrink by a certain amount (but not by as much as the
   recovered page will consume)

In other words, zram works a bit like a swap disk, but it also acts a 
bit like compressing data in RAM.


So, applications won't see a slowdown in memory access because they 
still talk directly to RAM. However, if an application has been swapped 
to zram, then decompressing the page from zram WILL be quicker than 
pulling the page from a block device, even an NVMe drive.




OpenPGP_signature.asc
Description: OpenPGP digital signature

Re: swap-fle on arm64, need to disable, how?

[Curt]

On 2023-10-01, gene heskett  wrote:
>> 
> Andy, with good luck, you may make to your 89th birthday, which with 
> good luck I'll celebrate next Wednesday.  I certainly hope you do. By 
> then you will not see any humor in trying to remember what, if anything, 
> you had for breakfast this morning. I seem to have reached that point. 
> And I'm not any happier for it either.

What are you building? A space ship to get out of here?

> Cheers, Gene Heskett.

Re: swap-fle on arm64, need to disable, how?

[Andrew M.A. Cater]

On Sun, Oct 01, 2023 at 08:58:36AM -0400, Greg Wooledge wrote:
> On Sun, Oct 01, 2023 at 05:07:48AM -0400, gene heskett wrote:
> > You've a good view of this hw. However swap is not important to run
> > linuxcnc, in fact its to be avoided because it messes with realtime
> > response. Linuxcnc needs, even with much of the control offloaded to mesa
> > and similar smart cards, it still needs to check what the machine is doing
> > 1000 times a second. The way I'm doing it, the wobble in this timing as 50
> > to 80 microseconds, which doesn't bother the machine all that much, the real
> > time killer is firing up firefox which can lock out the irq response for
> > hundreds of milliseconds.  So I don't carve metal and browse the web at the
> > same time.
> 
> If Firefox is really just for "browsing the web", and is not part of
> the user interface for the CNC pieces, I don't understand why you run
> Firefox on this machine at all.  I would run the browser on a separate
> computer, one which isn't so critical to your operation.
>

Echoing Greg:

2G is a fairly small amount of memory - by default the *Debian* install
for RPi 4 now gives you 1G of swap on whatever medium - which you should
never need to use.

It would make sense for something real time critical to be on a 2GB or 4GB RPi
on it's own - if you're running modellers or whatever for 3D printing, that
might be different but a command line or simplest web interface might be
best. You REALLY don't want anything extraneous.

Pi 4GB or 8GB are now available more or less: your BananaPi - you are *very*
much on your own.

All best, sa ever,

Andy
[amaca...@debian.org] 

Re: swap-fle on arm64, need to disable, how?

[Greg Wooledge]

On Sun, Oct 01, 2023 at 05:07:48AM -0400, gene heskett wrote:
> You've a good view of this hw. However swap is not important to run
> linuxcnc, in fact its to be avoided because it messes with realtime
> response. Linuxcnc needs, even with much of the control offloaded to mesa
> and similar smart cards, it still needs to check what the machine is doing
> 1000 times a second. The way I'm doing it, the wobble in this timing as 50
> to 80 microseconds, which doesn't bother the machine all that much, the real
> time killer is firing up firefox which can lock out the irq response for
> hundreds of milliseconds.  So I don't carve metal and browse the web at the
> same time.

If Firefox is really just for "browsing the web", and is not part of
the user interface for the CNC pieces, I don't understand why you run
Firefox on this machine at all.  I would run the browser on a separate
computer, one which isn't so critical to your operation.

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 10/1/23 04:05, Max Nikulin wrote:

On 01/10/2023 10:21, hw wrote:

Well, zram is the way to go; why would you still use swap partitions
or swap files instead?


The topic of this thread is a *Pi board. It does not have as much RAM as 
significant part of x86_64 laptops and desktops with installed Fedora.


It seems, Gene it trying to run some CNC software and Firefox to control 
it, perhaps some CAD. I suspect that some of mysterious issues are 
caused by not enough RAM. Adding swap on a hard drive instead of ZRAM 
may relief some issues.


However I would consider moving most of application to another machines. 
My suggestion is to monitor RAM usage and to avoid overloading of *Pi 
boards. Perhaps swap may be still necessary for complicated CNC tasks.


.
You've a good view of this hw. However swap is not important to run 
linuxcnc, in fact its to be avoided because it messes with realtime 
response. Linuxcnc needs, even with much of the control offloaded to 
mesa and similar smart cards, it still needs to check what the machine 
is doing 1000 times a second. The way I'm doing it, the wobble in this 
timing as 50 to 80 microseconds, which doesn't bother the machine all 
that much, the real time killer is firing up firefox which can lock out 
the irq response for hundreds of milliseconds.  So I don't carve metal 
and browse the web at the same time.  I added some dials and decoders so 
I can run this lathe, which only has 3 motors, and no compound at all, 
by hand using the dials as hand cranks. Originally doing this on an 
rpi3b when it was new in the 2017-2018 timeframe, I put all the hand 
control stuff in a slower 200 hz thread since I can't turn the dials any 
faster by hand anyway. Its still there. Linuxcnc, driving the two 
motors, is a far more accurate compound than the broken compound I've 
removed ever was.  The third motor is driving the spindle at 
continuously variable speeds with an encoder telling linuxcnc where the 
spindle is 240 times a revolution.  There are no change gears, yet it 
can cut any thread, inch or metric including some I've dreamed up. 
Sub-micron accurate at any angle.  Whats not to like?


Take care & stay well.

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 

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 23:22, hw wrote:

On Sat, 2023-09-30 at 18:29 -0400, gene heskett wrote:

On 9/30/23 13:28, Matthias Böttcher wrote:

sudo dphys-swapfile swapoff
sudo systemctl stop dphys-swapfile.service
sudo systemctl disable dphys-swapfile.service

.

However that did give me a clue about getting rid of zram0, which has
been done now, thank you. Now I hope to uncomment the SSD line in fstab.


Well, zram is the way to go; why would you still use swap partitions
or swap files instead?  Are you deliberately trying to wear out your
SSDs or to slow down your computer?

zram is probably the way to go for board with lots of dram. Something 
the pi's don't have. My only pi is an early rpi4b, Claims 2G, shows 
1.8G. I tend to do big things with it. I was first on this ball of rock 
and water to make linuxcnc and that pi, run an 80 yo lathe I converted 
to cnc controls. Teaching that lathe tricks it could not do when it 
shipped out out Chicago circa 1946.


To steal over a gig for zram style swap does not make any sense to me. 
There's compression and decompression involved too I'm told. By putting 
swap on a 10G partition on a 500meg a second SSD, brings big memory into 
the picture, allowing that little card to do big things without running 
out of memory. I've built its own realtime kernels on it is 23 minutes, 
linuxcnc with its docs including some translations ran it 200megs into 
that zram and took nearly 4 hours.  With real swap back on buster, just 
under an hour. Just the English docs are now over 1000 pages of dead 
tree. What we really need are translators. Except for the de stuff, 
other languages are quite incomplete, but this old Iowa farm kid doesn't 
speak anything but English, and doesn't even touch type.


I'm not a "working shop" other than my own product, just a retired bc 
engineer. I basically serve as the canary in the coal mine for linuxcnc, 
keeping that pi up to date with the git master & looking for 
showstoppers. This gets done several times a week, doing a decent job of 
keeping me out of the bars.



Fedora has it by default since a while, and at first I thought it's a
very stupid idea.  In practise, I can't be bothered anymore to create
these annoying swap partitions.  They're only a waste of disc space.
There haven't been any issues with it, and when the machine runs out
of memory, using swap partitions or swap files isn't going to fix
that.


But with zram  taking over half its memory, its into swap and slowing 
down quicker, and plumb out of memory for big jobs, when it could still 
be working fine with bigger, albeit probably slower than zram, swap.


I've no clue how much the zram compression slows it in terms of thru put.

I wiped out the git clone of linuxcnc by re-arranging that SSD 
yesterday, but I'll do another build later today and see how long it 
takes with real swap.


Thank you. Take care & stay well.


.


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 

Re: swap-fle on arm64, need to disable, how?

[Max Nikulin]

On 01/10/2023 01:16, Greg Wooledge wrote:

On Sat, Sep 30, 2023 at 01:50:57PM -0400, gene heskett wrote:

cnc@rpi4:/etc$ sudo dphys-swapfile swapoff
sudo: dphys-swapfile: command not found

...

unicorn:~$ apt-cache search dphys swap
dphys-swapfile - Autogenerate and use a swap file


From my point of view, "command not found" is a clear sign that 
/dev/zram0 is created by some other package. I have never tried to setup 
ZRAM, so I have no idea if some amount of RAM may be preallocated even 
when /dev/zram0 is not added to swap. From my point of view, instead of 
installing additional packages, it is better to find its current 
configuration. At least it will ensure that all RAM is available for 
applications.


I posted a link to ArchLinux wiki with hope that it may contain some 
hints how to configure ZRAM and thus how to disable it.

Re: swap-fle on arm64, need to disable, how?

[Max Nikulin]

On 01/10/2023 10:21, hw wrote:

Well, zram is the way to go; why would you still use swap partitions
or swap files instead?


The topic of this thread is a *Pi board. It does not have as much RAM as 
significant part of x86_64 laptops and desktops with installed Fedora.


It seems, Gene it trying to run some CNC software and Firefox to control 
it, perhaps some CAD. I suspect that some of mysterious issues are 
caused by not enough RAM. Adding swap on a hard drive instead of ZRAM 
may relief some issues.


However I would consider moving most of application to another machines. 
My suggestion is to monitor RAM usage and to avoid overloading of *Pi 
boards. Perhaps swap may be still necessary for complicated CNC tasks.

Re: swap-fle on arm64, need to disable, how?

[hw]

On Sat, 2023-09-30 at 18:29 -0400, gene heskett wrote:
> On 9/30/23 13:28, Matthias Böttcher wrote:
> > sudo dphys-swapfile swapoff
> > sudo systemctl stop dphys-swapfile.service
> > sudo systemctl disable dphys-swapfile.service
> > 
> > .
> However that did give me a clue about getting rid of zram0, which has 
> been done now, thank you. Now I hope to uncomment the SSD line in fstab.

Well, zram is the way to go; why would you still use swap partitions
or swap files instead?  Are you deliberately trying to wear out your
SSDs or to slow down your computer?

Fedora has it by default since a while, and at first I thought it's a
very stupid idea.  In practise, I can't be bothered anymore to create
these annoying swap partitions.  They're only a waste of disc space.
There haven't been any issues with it, and when the machine runs out
of memory, using swap partitions or swap files isn't going to fix
that.

Re: swap-fle on arm64, need to disable, how?

[Stefan Monnier]

> But I cannot label the partition.  At least not with gparted.  I did
> generate a new blkid then put the partuuid in fstab, rebooted it and
> that worked.

This sounds to me like a subliminal message telling me "see all the pain
you avoided by using LVM instead".


Stefan

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 16:15, Andy Smith wrote:

Hello,

On Sat, Sep 30, 2023 at 11:15:18AM -0400, gene heskett wrote:

On 9/30/23 07:46, Andy Smith wrote:

On Sat, Sep 30, 2023 at 03:26:19AM -0400, gene heskett wrote:

On 9/29/23 17:32, Andy Smith wrote:

On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:

Swap file is the last thing I want, much slower than a swap partition.


There has been no performance difference between swap files and
swap partitions for more than a decade.


Maybe on wintel stuff, but the u-sd card the pi runs on has a write speed
below 10 megs/second, an extremely obvious performance hit, and wearing out
the u-sd card rapidly.


Please show evidence or retract your claim that on a raspberry pi a
swap partition performs better than a swap file (when they are both
on the same storage device). I believe you are making it up, as it
isn't the case in the kernel code and should not make any difference
by architecture.


There is a huge difference in the write speeds between a modern SSD that can
be written at usb3 speeds, and the write speed of a micro-sd card the pi
boots from.

This is a real world fact Andy C. Tested, verified FACT.


This has become very silly now, or maybe tragic is a more suitable
description. All you have to do is look back at what you have
actually written as quoted above, or in the archives of this thread.

Except where I've paraphrased in [], the following are actual
verbatim words typed by you and I here in this thread on this list.

You said: I have SSD's for swap on an rpi4b, so to lessen the abuse
   of the u-sd card I need to turn off the swap file, and
   swapon -a the SSD stuff.

I said: If the swap file is listed in [your fstab], remove it and
 add one that's on your SSD.

You replied: Swap file is the last thing I want, much slower than a
  swap partition.

No one, at any point, told you to put a swap file on an SD card. No
one, at any point, said that SD cards perform the same as SSDs.

What you have said above is that swap files are slower than swap
partitions. When corrected on this, you start saying that SD cards
are slower than SSDs, which is not a claim that anyone has disputed,
nor would anyone sensibly dispute it.

I'm surprised that you do not consider it odd that you find yourself
having to explain to someone that SD cards are slower than SSDs, and
that you do not question why that has happened. I personally am
finding it alarming that I'm having to point out to someone what
words they used two emails back in the same thread. I'm starting to
feel like neither of us are having a good time and we should stop.


Testimony from one of the maintainers of the memory management and
ext filesystems in the Linux kernel:

  https://lkml.org/lkml/2005/6/29/11
  https://lkml.org/lkml/2005/7/7/326


TL,DR, my experience is a fact.


You're having arguments about things that have never been claimed;
I'm having arguments about things you don't even remember writing,
and refuse to read again to refresh your memory. I'm genuinely sorry
to see it has got to this stage and I think it's best if I leave
this particular debate there.

I don't know what to do any more when you post misinformation to the
list. If we're now at a stage where you can't be conversed with
because you don't remember what you've posted even a few emails ago
and won't read back your own emails, it's not possible to convince
you of your error. But on the other hand, it often hasn't been
possible to convince you of your errors on many topics for many
years, so I suppose that can't be and should never have been the
goal. I think perhaps best to just try my best to not enter into any
debate.

Thanks,
Andy

Andy, with good luck, you may make to your 89th birthday, which with 
good luck I'll celebrate next Wednesday.  I certainly hope you do. By 
then you will not see any humor in trying to remember what, if anything, 
you had for breakfast this morning. I seem to have reached that point. 
And I'm not any happier for it either.


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 

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 14:16, Greg Wooledge wrote:

search dphys swap

Something I need to learn. But its been yonks since I last needed that.
Anyway, problem is solved,  Thank you. Take care ad stay well.

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 

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 13:28, Matthias Böttcher wrote:

sudo dphys-swapfile swapoff
sudo systemctl stop dphys-swapfile.service
sudo systemctl disable dphys-swapfile.service

.
However that did give me a clue about getting rid of zram0, which has 
been done now, thank you. Now I hope to uncomment the SSD line in fstab.


So I've re-partitioned & reformatted the 120G SSD to a gpt partition 
table eith 10G of swap and a hair over 110G of ext4 for workspace.
But that is still no good. I can sudo swapon /dev/sda1 & sudo swapon -a 
now works, but sudo swapon -s returns nothing. But I cannot label the 
partition.  At least not with gparted.  I did generate a new blkid then 
put the partuuid in fstab, rebooted it and that worked.


So this problem is solved. Until something changes the partuid.

Thanks for putting up with me.
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 

Re: swap-fle on arm64, need to disable, how?

[Andy Smith]

Hello,

On Sat, Sep 30, 2023 at 11:15:18AM -0400, gene heskett wrote:
> On 9/30/23 07:46, Andy Smith wrote:
> > On Sat, Sep 30, 2023 at 03:26:19AM -0400, gene heskett wrote:
> > > On 9/29/23 17:32, Andy Smith wrote:
> > > > On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:
> > > > > Swap file is the last thing I want, much slower than a swap partition.
> > > > 
> > > > There has been no performance difference between swap files and
> > > > swap partitions for more than a decade.
> > > 
> > > Maybe on wintel stuff, but the u-sd card the pi runs on has a write speed
> > > below 10 megs/second, an extremely obvious performance hit, and wearing 
> > > out
> > > the u-sd card rapidly.
> > 
> > Please show evidence or retract your claim that on a raspberry pi a
> > swap partition performs better than a swap file (when they are both
> > on the same storage device). I believe you are making it up, as it
> > isn't the case in the kernel code and should not make any difference
> > by architecture.
> 
> There is a huge difference in the write speeds between a modern SSD that can
> be written at usb3 speeds, and the write speed of a micro-sd card the pi
> boots from.
> 
> This is a real world fact Andy C. Tested, verified FACT.

This has become very silly now, or maybe tragic is a more suitable
description. All you have to do is look back at what you have
actually written as quoted above, or in the archives of this thread.

Except where I've paraphrased in [], the following are actual
verbatim words typed by you and I here in this thread on this list.

You said: I have SSD's for swap on an rpi4b, so to lessen the abuse
  of the u-sd card I need to turn off the swap file, and
  swapon -a the SSD stuff.

I said: If the swap file is listed in [your fstab], remove it and
add one that's on your SSD.

You replied: Swap file is the last thing I want, much slower than a
 swap partition.

No one, at any point, told you to put a swap file on an SD card. No
one, at any point, said that SD cards perform the same as SSDs.

What you have said above is that swap files are slower than swap
partitions. When corrected on this, you start saying that SD cards
are slower than SSDs, which is not a claim that anyone has disputed,
nor would anyone sensibly dispute it.

I'm surprised that you do not consider it odd that you find yourself
having to explain to someone that SD cards are slower than SSDs, and
that you do not question why that has happened. I personally am
finding it alarming that I'm having to point out to someone what
words they used two emails back in the same thread. I'm starting to
feel like neither of us are having a good time and we should stop.

> > Testimony from one of the maintainers of the memory management and
> > ext filesystems in the Linux kernel:
> > 
> >  https://lkml.org/lkml/2005/6/29/11
> >  https://lkml.org/lkml/2005/7/7/326
> 
> TL,DR, my experience is a fact.

You're having arguments about things that have never been claimed;
I'm having arguments about things you don't even remember writing,
and refuse to read again to refresh your memory. I'm genuinely sorry
to see it has got to this stage and I think it's best if I leave
this particular debate there.

I don't know what to do any more when you post misinformation to the
list. If we're now at a stage where you can't be conversed with
because you don't remember what you've posted even a few emails ago
and won't read back your own emails, it's not possible to convince
you of your error. But on the other hand, it often hasn't been
possible to convince you of your errors on many topics for many
years, so I suppose that can't be and should never have been the
goal. I think perhaps best to just try my best to not enter into any
debate.

Thanks,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

Re: swap-fle on arm64, need to disable, how?

[Matthias Böttcher]

Hi Gene,

please check explanations in this blog:
https://www.dwarmstrong.org/zram-linuxmint/

HTH
Matthias

gene heskett  schrieb am Sa., 30. Sept. 2023, 19:51:

> On 9/30/23 13:28, Matthias Böttcher wrote:
> > sudo dphys-swapfile swapoff
> > sudo systemctl stop dphys-swapfile.service
> > sudo systemctl disable dphys-swapfile.service
> >
> > .
> Looks familiar but none of that is installed
> cnc@rpi4:/etc$ sudo dphys-swapfile swapoff
> sudo: dphys-swapfile: command not found
> cnc@rpi4:/etc$ sudo systemctl stop dphys-swapfile.service
> Failed to stop dphys-swapfile.service: Unit dphys-swapfile.service not
> loaded.
> cnc@rpi4:/etc$ sudo systemctl disable dphys-swapfile.service
> Failed to disable unit: Unit file dphys-swapfile.service does not exist.
>
> What I'm trying to do is get rid of zram0, which is being used as swap,
> and sub real swap on an SSD in its place. And zram0 is not listed in
> fstab, but swapon finds it.
>
> Thank you, Matthias Böttcher
>
> 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 
>
>

Re: swap-fle on arm64, need to disable, how?

[Greg Wooledge]

On Sat, Sep 30, 2023 at 01:50:57PM -0400, gene heskett wrote:
> On 9/30/23 13:28, Matthias Böttcher wrote:
> > sudo dphys-swapfile swapoff
> > sudo systemctl stop dphys-swapfile.service
> > sudo systemctl disable dphys-swapfile.service
> > 
> > .
> Looks familiar but none of that is installed
> cnc@rpi4:/etc$ sudo dphys-swapfile swapoff
> sudo: dphys-swapfile: command not found
> cnc@rpi4:/etc$ sudo systemctl stop dphys-swapfile.service
> Failed to stop dphys-swapfile.service: Unit dphys-swapfile.service not
> loaded.
> cnc@rpi4:/etc$ sudo systemctl disable dphys-swapfile.service
> Failed to disable unit: Unit file dphys-swapfile.service does not exist.

Come now, you should be able to figure this shit out by now, Gene.

unicorn:~$ apt-cache search dphys swap
dphys-swapfile - Autogenerate and use a swap file

I've never even HEARD of this thing before, and I can figure out to run
a basic command to search for the right package.

Now, whether running those dphys commands is GOOD or USEFUL is an
entirely different question.  But you should have the basic competence
to do an "apt(-cache) search" by now.

Re: swap-fle on arm64, need to disable, how?

[David Wright]

On Sat 30 Sep 2023 at 03:26:19 (-0400), gene heskett wrote:
> On 9/29/23 17:32, Andy Smith wrote:
> > On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:
> > > cnc@rpi4:/etc$ sudo swapon -s
> > > FilenameTypeSize Used
> > > Priority
> > > /dev/zram0  partition   1048572 98304
> > > 100
> > > /dev/sda2   partition   9859068 0
> > > -3
> > > 
> > > I need it to forget zram0 and use the swap on sda2
> > 
> > You didn't respond to the part about /etc/fstab so we have no idea
> > if you found the information you needed.
> 
> I didn't find the swap listed in the fstab, its apparently setup
> someplace else in debian 12 for arm64's, so I've not finalized that
> yet.  Awaiting guidance.
> 
> > Assuming you did find the errant entry in /etc/fstab, a sequence of:
> > 
> > 1. swapoff -a
> > 2. edit /etc/fstab to be correct
> > 3. swapon -a
> 
> I'd also point out that despite the presence of the above listed swap,
> swapon -a and swapoff -a, does not enable it, I have to mount it by
> hand.
> > 
> > should change things to how you want them.

IMO you're being blinded by /etc/fstab and -a. Rather, use /proc/swaps
to see what the kernel knows, and stop using -a. Cut and paste what
you do and the output, rather than all this "doesn't work" etc.

I'm guessing that on a parallel track, you need to examine the startup
files of whatever this beast is, presumably not Debian, and find some
occurrence of swapon that you can, in your jargon, "nuke".

Cheers,
David.

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 13:28, Matthias Böttcher wrote:

sudo dphys-swapfile swapoff
sudo systemctl stop dphys-swapfile.service
sudo systemctl disable dphys-swapfile.service

.

Looks familiar but none of that is installed
cnc@rpi4:/etc$ sudo dphys-swapfile swapoff
sudo: dphys-swapfile: command not found
cnc@rpi4:/etc$ sudo systemctl stop dphys-swapfile.service
Failed to stop dphys-swapfile.service: Unit dphys-swapfile.service not 
loaded.

cnc@rpi4:/etc$ sudo systemctl disable dphys-swapfile.service
Failed to disable unit: Unit file dphys-swapfile.service does not exist.

What I'm trying to do is get rid of zram0, which is being used as swap, 
and sub real swap on an SSD in its place. And zram0 is not listed in 
fstab, but swapon finds it.


Thank you, Matthias Böttcher

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 

Re: swap-fle on arm64, need to disable, how?

[Matthias Böttcher]

sudo dphys-swapfile swapoff
sudo systemctl stop dphys-swapfile.service
sudo systemctl disable dphys-swapfile.service

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/30/23 07:46, Andy Smith wrote:

Hello,

On Sat, Sep 30, 2023 at 03:26:19AM -0400, gene heskett wrote:

On 9/29/23 17:32, Andy Smith wrote:

On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:

Swap file is the last thing I want, much slower than a swap partition.


There has been no performance difference between swap files and
swap partitions for more than a decade.


Maybe on wintel stuff, but the u-sd card the pi runs on has a write speed
below 10 megs/second, an extremely obvious performance hit, and wearing out
the u-sd card rapidly.


Please show evidence or retract your claim that on a raspberry pi a
swap partition performs better than a swap file (when they are both
on the same storage device). I believe you are making it up, as it
isn't the case in the kernel code and should not make any difference
by architecture.


There is a huge difference in the write speeds between a modern SSD that 
can be written at usb3 speeds, and the write speed of a micro-sd card 
the pi boots from.


This is a real world fact Andy C. Tested, verified FACT.

For small writes it might approach the BS claims on the blister card but 
rarely gets there, for megabyte and up writes its often below 10 megs a 
second. The blister card may claim up to 120M/S, but dd shows that 
outright lie when imaging a 64GB card with a 7G image, doing the last 
75% of that 7G at less then 10M/S.  On raspios-wheezy, swap was on the 
u-sd card. And it took me 3 hours & change to build a realtime preempt 
4.19 kernel for the pi, on the pi.  Switch the swap to a sata-iii SSD on 
a startech usb3-sata adapter, and that same kernel build is 23 minutes 
on the pi, for the pi.



Testimony from one of the maintainers of the memory management and
ext filesystems in the Linux kernel:

 https://lkml.org/lkml/2005/6/29/11
 https://lkml.org/lkml/2005/7/7/326


TL,DR, my experience is a fact. The medium differences which you keep 
ignoring, is in FACT important.



Swapping on SD cards in general is a bad idea regardless of
architecture, but there should be no difference between swap file or
swap partition. I did not suggest you swap to a file on SD card. I
suggested that whether you swap to a file on SSD or a partition on
SSD, the performance will be the same.


True, as long as both are on the SAME medium. However my experience with 
swap files on pi's has been with swap files on the u-sd. They do work, 
If you plan on a long nap while they work, and the u-sd card doesn't 
wear out, which I have had happen on smaller cards. That upset me, a lot 
as I had to rewrite a couple gigs of gcode that disappeared.  That 
taught me to include the pi in my amanda backups. Then I bought two 
seacrate 2T rust buckets, spent about 6 weeks building up a buster on 
the new, faster drives. And both drives disappeared off the end of the 
cables 4 days apart a week later losing everything. Junk I didn't even 
try to warranty. Burn me a third time and I'm all done with that name on 
the box. Now I'm collecting 2T gigastones to do it again, about the same 
price as the SamSung's, but turn them over and read "made in Taiwan"


Its been hell trying to make bookworm usable.  And I seem to be headed 
to do it again, the raid10 I built on bullseye for /home, is not 
compatible with bookworm and no one can tell me what to do to fix it. 
The problem is that ANYTHING that wants write access to that raid10 has 
to wait anywhere from 30 seconds to 5 minutes to open the requestor. It 
always works, all I have to do is wait, then wait some more. Wash, rinse 
and repeat.  That's BS and you all wonder why I am in such a bad mood.


It's also a puzzle. I have an AppImages directory off of /home/gene on 
that raid10, and those AppImages work as instantly as one would expect 
from a raid10 made of 4 1T SamSung 870 SSD's. 2, maybe 3 seconds to a 
fully drawn screen ready to do work. Yet when one of those apps want to 
write, its always blocked the first time by this wait but not there 
after. But leave it running overnight, wash, rinse, repeat the delay 
again the next day.  Why?



Here is the current fstab:
  cnc@rpi4:~$ cat /etc/fstab
UUID=8E25-4B18  /boot/broadcom  vfat defaults,flush
0 2
UUID=47946eb6-d88c-4331-bba9-cbe269a35925   /   ext4
defaults,noatime,commit=600,errors=remount-ro 0 1
tmpfs   /tmptmpfs
defaults,nosuid 0 0
# to which I've added but commented ATM
#LABEL=TEMP1/tmpext4
defaults,noatime,errors=remount-ro 0 1


There's no swap listed there and the only thing you've added seems
to have a comment in front of it, so you've effectively added
nothing so I don't understand why you expect something to change now.


cnc@rpi4:/etc$ sudo swapon -s
FilenameTypeSize Used
Priority
/dev/zram0  partition   1048572 98304
100
/dev/sda2   partition   

Re: swap-fle on arm64, need to disable, how?

[Andy Smith]

Hello,

On Sat, Sep 30, 2023 at 03:26:19AM -0400, gene heskett wrote:
> On 9/29/23 17:32, Andy Smith wrote:
> > On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:
> > > Swap file is the last thing I want, much slower than a swap partition.
> > 
> > There has been no performance difference between swap files and
> > swap partitions for more than a decade.
> 
> Maybe on wintel stuff, but the u-sd card the pi runs on has a write speed
> below 10 megs/second, an extremely obvious performance hit, and wearing out
> the u-sd card rapidly.

Please show evidence or retract your claim that on a raspberry pi a
swap partition performs better than a swap file (when they are both
on the same storage device). I believe you are making it up, as it
isn't the case in the kernel code and should not make any difference
by architecture.

Testimony from one of the maintainers of the memory management and
ext filesystems in the Linux kernel:

https://lkml.org/lkml/2005/6/29/11
https://lkml.org/lkml/2005/7/7/326

Swapping on SD cards in general is a bad idea regardless of
architecture, but there should be no difference between swap file or
swap partition. I did not suggest you swap to a file on SD card. I
suggested that whether you swap to a file on SSD or a partition on
SSD, the performance will be the same.

> Here is the current fstab:
>  cnc@rpi4:~$ cat /etc/fstab
> UUID=8E25-4B18  /boot/broadcom  vfat defaults,flush
> 0 2
> UUID=47946eb6-d88c-4331-bba9-cbe269a35925   /   ext4
> defaults,noatime,commit=600,errors=remount-ro 0 1
> tmpfs   /tmptmpfs
> defaults,nosuid 0 0
> # to which I've added but commented ATM
> #LABEL=TEMP1/tmpext4
> defaults,noatime,errors=remount-ro 0 1

There's no swap listed there and the only thing you've added seems
to have a comment in front of it, so you've effectively added
nothing so I don't understand why you expect something to change now.

> > > cnc@rpi4:/etc$ sudo swapon -s
> > > FilenameTypeSize Used
> > > Priority
> > > /dev/zram0  partition   1048572 98304
> > > 100
> > > /dev/sda2   partition   9859068 0
> > > -3
> > > 
> > > I need it to forget zram0 and use the swap on sda2
> > 
> > You didn't respond to the part about /etc/fstab so we have no idea
> > if you found the information you needed.
> 
> I didn't find the swap listed in the fstab, its apparently setup someplace
> else in debian 12 for arm64's, so I've not finalized that yet.  Awaiting
> guidance.

This isn't Debian 12 though is it? Debian doesn't use zram by
default so this is something else. As usual we struggle to answer
your questions as they're off-topic here, amongst other
difficulties.

As the other poster mentioned, zram is set up by a systemd unit but I
don't know more about it off the top of my head.

> > 1. swapoff -a
> > 2. edit /etc/fstab to be correct
> > 3. swapon -a
> 
> I'd also point out that despite the presence of the above listed swap,
> swapon -a and swapoff -a, does not enable it, I have to mount it by hand.

As I said, your fstab as shown does not contain any reference to
swap, so I'm not surprised that you have to manually tell it to use
/dev/sda2.

First tackle disabling the zram (or making it use sda2).

Thanks,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/29/23 17:32, Andy Smith wrote:

Hello,

On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:

On 9/29/23 15:21, Andy Smith wrote:

On Fri, Sep 29, 2023 at 03:15:54PM -0400, gene heskett wrote:

I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd card I
need to turn off the swap file, and swapon -a the SSD stuff.


Have you looked in /etc/fstab where as you know filesystem mounts
are described? If the swap file is listed in there, remove it and
add one that's on your SSD.


[…]


Swap file is the last thing I want, much slower than a swap partition.


There has been no performance difference between swap files and
swap partitions for more than a decade.


Maybe on wintel stuff, but the u-sd card the pi runs on has a write 
speed below 10 megs/second, an extremely obvious performance hit, and 
wearing out the u-sd card rapidly.


But is swap on an rpi4b not on the sd card? as an invisible swap file? 
If so there is an obvious speed hit and that sort of use would be hell 
on the u-sd card. I long ago converted the buster install so such swap 
was all on an SSD.


Here is that fstab from the buster install:
cnc@rpi4:~$ cat /sdb2/etc/fstab
proc/proc   procdefaults  0   0
PARTUUID=5e3da3da-01  /boot   vfatdefaults  0   2
PARTUUID=5e3da3da-02  /   ext4defaults,noatime  0   1
# a swapfile is not a swap partition, no line here
#   use  dphys-swapfile swap[on|off]  for that
UUID=746054d4-9a33-4c79-b028-ffc3e40a none swap 0 0
PARTUUID=c61252a1-01  /media/pi/workspace ext4 defaults 0 1
the swap is 10Gigs worth of a 120G SSD on a startech usb/sata thing
and workspace is most of a 240G SSD on a startech usb/sata adapter with 
r/w speeds of 4 or 5 hundred megs and write speeds in the 300 range. I 
could build lcnc in 30 minutes on that pi. Or a new copy of that kernel 
in 23 minutes. And never touch the u-sd card until I installed the debs 
for a new lcnc 2 or 3 times a week.


Here is the current fstab:
 cnc@rpi4:~$ cat /etc/fstab
UUID=8E25-4B18  /boot/broadcom  vfat 
defaults,flush 0 2
UUID=47946eb6-d88c-4331-bba9-cbe269a35925   /   ext4 
defaults,noatime,commit=600,errors=remount-ro 0 1
tmpfs   /tmptmpfs 
defaults,nosuid 0 0

# to which I've added but commented ATM
#LABEL=TEMP1/tmpext4 
defaults,noatime,errors=remount-ro 0 1


The label is good, but is the ext4? Thats the format of /dev/sda4
/dev/sda2 is currently mounted as swap, hows below but was not mounted 
when I built linuxcnc yesterday. runtests ran normally, so I did a make 
clean and built debs, but haven't installed them.



cnc@rpi4:/etc$ sudo swapon -s
FilenameTypeSize Used
Priority
/dev/zram0  partition   1048572 98304
100
/dev/sda2   partition   9859068 0
-3

I need it to forget zram0 and use the swap on sda2


You didn't respond to the part about /etc/fstab so we have no idea
if you found the information you needed.


I didn't find the swap listed in the fstab, its apparently setup 
someplace else in debian 12 for arm64's, so I've not finalized that yet. 
 Awaiting guidance.



Assuming you did find the errant entry in /etc/fstab, a sequence of:

1. swapoff -a
2. edit /etc/fstab to be correct
3. swapon -a


I'd also point out that despite the presence of the above listed swap, 
swapon -a and swapoff -a, does not enable it, I have to mount it by hand.


should change things to how you want them.

Thanks,
Andy


Take care & stay well, Andy.

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 

Re: swap-fle on arm64, need to disable, how?

[Max Nikulin]

On 30/09/2023 03:36, gene heskett wrote:

On 9/29/23 15:21, Andy Smith wrote:


On Fri, Sep 29, 2023 at 03:15:54PM -0400, gene heskett wrote:
I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd 



cnc@rpi4:/etc$ sudo swapon -s
Filename    Type    Size 
Used    Priority
/dev/zram0  partition   1048572 
98304   100
/dev/sda2   partition   9859068 
0   -3


I need it to forget zram0 and use the swap on sda2


Out of curiosity, is zram0 really belongs to the SD card or it is 
compressed pages in RAM?


Besides fstab it might be configured through a systemd .mount target.

Accordingly to https://wiki.archlinux.org/title/Zram it requires more 
configuration however.

Re: swap-fle on arm64, need to disable, how?

[Andy Smith]

Hello,

On Fri, Sep 29, 2023 at 04:36:04PM -0400, gene heskett wrote:
> On 9/29/23 15:21, Andy Smith wrote:
> > On Fri, Sep 29, 2023 at 03:15:54PM -0400, gene heskett wrote:
> > > I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd 
> > > card I
> > > need to turn off the swap file, and swapon -a the SSD stuff.
> > 
> > Have you looked in /etc/fstab where as you know filesystem mounts
> > are described? If the swap file is listed in there, remove it and
> > add one that's on your SSD.

[…]

> Swap file is the last thing I want, much slower than a swap partition.

There has been no performance difference between swap files and
swap partitions for more than a decade.

> cnc@rpi4:/etc$ sudo swapon -s
> FilenameTypeSize Used
> Priority
> /dev/zram0  partition   1048572 98304
> 100
> /dev/sda2   partition   9859068 0
> -3
> 
> I need it to forget zram0 and use the swap on sda2

You didn't respond to the part about /etc/fstab so we have no idea
if you found the information you needed.

Assuming you did find the errant entry in /etc/fstab, a sequence of:

1. swapoff -a
2. edit /etc/fstab to be correct
3. swapon -a

should change things to how you want them.

Thanks,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

Re: swap-fle on arm64, need to disable, how?

[gene heskett]

On 9/29/23 15:21, Andy Smith wrote:

Hello,

On Fri, Sep 29, 2023 at 03:15:54PM -0400, gene heskett wrote:

I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd card I
need to turn off the swap file, and swapon -a the SSD stuff.


Have you looked in /etc/fstab where as you know filesystem mounts
are described? If the swap file is listed in there, remove it and
add one that's on your SSD.

If it's not in there, the situation is more of a mystery and I'd
suggest you paste the output of "swapon -s" so we can see what the
system, thinks it is currently swapping to.

I assume you don't need instruction on how to turn off an existing
swap source, and how to create a new swap file.


Swap file is the last thing I want, much slower than a swap partition.


Thanks,
Andy


cnc@rpi4:/etc$ sudo swapon -s
FilenameTypeSize 
UsedPriority
/dev/zram0  partition   1048572 
98304   100
/dev/sda2   partition   9859068 
0   -3


I need it to forget zram0 and use the swap on sda2, although I may try 
to move /tmp to sda4 & ext4 now that I know how to run gparted on wayland.


Whats in zram0 ATM is lose able as I just built linuxcnc debs, docs and 
all from a git clone.


Thanks Andy.

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 

Re: swap-fle on arm64, need to disable, how?

[Andy Smith]

Hello,

On Fri, Sep 29, 2023 at 03:15:54PM -0400, gene heskett wrote:
> I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd card I
> need to turn off the swap file, and swapon -a the SSD stuff.

Have you looked in /etc/fstab where as you know filesystem mounts
are described? If the swap file is listed in there, remove it and
add one that's on your SSD.

If it's noit in there, the situation is more of a mystery and I'd
suggest you paste the output of "swapon -s" so we can see what the
system, thinks it is currently swapping to.

I assume you don't need instruction on how to turn off an existing
swap source, and how to create a new swap file.

Thanks,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

swap-fle on arm64, need to disable, how?

[gene heskett]

Greetings all;

I have SSD's for swap on an rpi4b, so to lessen the abuse of the u-sd 
card I need to turn off the swap file, and swapon -a the SSD stuff.


How?

Thnaks all.

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