Author Topic: OS/4 (technical details only)  (Read 177151 times)

OS4User

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Re: OS/4 (technical details only)
« Reply #270 on: August 22, 2023, 09:33:26 pm »
hi

I assume the OS/4 kernel also has to swttch to PAE mode and back to 4 GB adress mode (do not know the proper term).
How often does this switch occur ?

OS/4 does not use PAE.

What is the difference in peformance between Dixie his ram disc wih HPFS and the OS4KRNL ?

I have not heard that somebody tested it, me neither.

Is the difference you have no IFS layer ? Is this raw traffic to the ram disc ?

No IFS, no ram disc - just a direct swap with 4Gb+ memory ( using  memcpy ).


Roderick Klein

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Re: OS/4 (technical details only)
« Reply #271 on: August 22, 2023, 10:15:30 pm »
hi

I assume the OS/4 kernel also has to swttch to PAE mode and back to 4 GB adress mode (do not know the proper term).
How often does this switch occur ?

OS/4 does not use PAE.

What is the difference in peformance between Dixie his ram disc wih HPFS and the OS4KRNL ?

I have not heard that somebody tested it, me neither.

Is the difference you have no IFS layer ? Is this raw traffic to the ram disc ?

No IFS, no ram disc - just a direct swap with 4Gb+ memory ( using  memcpy ).

But the OS/4 kernel does access the memory above the 4GB memory region with PAE.
How is this done then ?

Roderick

OS4User

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Re: OS/4 (technical details only)
« Reply #272 on: August 22, 2023, 11:08:52 pm »
But the OS/4 kernel does access the memory above the 4GB memory region with PAE.

Again, the same answer: OS/4 does not use PAE at all

How is this done then ?

OS/4 uses a 36-bit page size extension (PSE-36)


Roderick Klein

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Re: OS/4 (technical details only)
« Reply #273 on: August 22, 2023, 11:19:57 pm »
But the OS/4 kernel does access the memory above the 4GB memory region with PAE.

Again, the same answer: OS/4 does not use PAE at all

How is this done then ?

OS/4 uses a 36-bit page size extension (PSE-36)

Does the CPU permanently run in PSE-36 mdoe ? Or do you switch between the 32 bitr mode and PSE-36 mode ?

Roderick

P.S. Thank you for answering my questions. 

OS4User

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Re: OS/4 (technical details only)
« Reply #274 on: August 22, 2023, 11:21:30 pm »
Does the CPU permanently run in PSE-36 mdoe ? Or do you switch between the 32 bitr mode and PSE-36 mode ?

permanently

Dave Yeo

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Re: OS/4 (technical details only)
« Reply #275 on: August 22, 2023, 11:52:53 pm »
Wiki has a quick explanation about PSE-36 mode, https://en.wikipedia.org/wiki/PSE-36 seems fine for a ram disk (and likely for swap support as the 4MB page size wouldn't matter) but not so good as a PAE replacement

Dariusz Piatkowski

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Re: OS/4 (technical details only)
« Reply #276 on: August 23, 2023, 04:15:56 am »
OS/4 Kernel swaps memory directly with 4Gb+ region, without involving IFS, etc. (starting from ver 6254 ).

No setup is necessary. If  4Gb+ mem is installed, 1.2Gb of it  will be used for swapping.

Enjoy a really fast swapping.

Nice!

...what happens if I had allocated some of that space to a RAMDISK? Will that config be respected, or is it that I effectively lose that space in my RAMDISK?

OS4User

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Re: OS/4 (technical details only)
« Reply #277 on: August 23, 2023, 09:52:09 am »
...what happens if I had allocated some of that space to a RAMDISK? Will that config be respected, or is it that I effectively lose that space in my RAMDISK?

If you run OS/4, only emsFS.ifs based ramdisk will work with 4Gb+ mem.

OS4User

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Re: OS/4 (technical details only)
« Reply #278 on: August 23, 2023, 10:34:04 am »
Wiki has a quick explanation about PSE-36 mode, https://en.wikipedia.org/wiki/PSE-36 seems fine for a ram disk (and likely for swap support as the 4MB page size wouldn't matter) but not so good as a PAE replacement

In our case it  has  sense  to compare PAE and PSE-36 in a OS/2 scope but not globally.

In fact  - os/2 drivers and kernel expect that physical addresses  are 32 bit width. (It is possible to change but huge amount of code has to be completely rewritten.)

Thus, 4Gb+ memory can be used for ramdisk or swap area only (almost).

OS/4 Team  to access 4Gb+ mem  chose PSE-36 for certain reasons:  access will be faster and simpler.

In case PDD and kernel gets transited to 64 bit physical addresses, PAE will be more suitable for sure.

Separately, I want to stress, transit to 64 bit physical addresses will not give some tangible gain - rather a loss.  PAE pte is twice bigger then PSE-36 one. Thus, page tables will consume twice more memory (and address space too).  And the system will remain 32 bits and all the problems of insufficient address space will remain.  So it is senseless.

Bernhard Pöttinger

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Re: OS/4 (technical details only)
« Reply #279 on: August 30, 2023, 10:33:00 am »
...what happens if I had allocated some of that space to a RAMDISK? Will that config be respected, or is it that I effectively lose that space in my RAMDISK?

If you run OS/4, only emsFS.ifs based ramdisk will work with 4Gb+ mem.

Hi OS4User,
how does the ramdisk (emsFS) work together with OS4kenrel PSE-36. My Notebook has 8GB, the emsfs ramdisk ist about 4,5GB; when I define a ramdisk with emsFS how does the kernel share the ramdisk?
bernhard

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Re: OS/4 (technical details only)
« Reply #280 on: August 31, 2023, 10:12:03 am »
Hi Bernhard

So far OS/4 kernel takes 1200Mb of 4Gb+ mem for swapping,  emsFS.ifs takes the rest.

Bernhard Pöttinger

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Re: OS/4 (technical details only)
« Reply #281 on: September 03, 2023, 12:15:14 pm »
Hello OS4User,

I have updated my OS4 kernel to the latest version and now my system does not start anymore. After "REINITDDs" boot stops; the machine is not complete dead; with Ctrl+Alt+Del I can restart it.

best regards
Bernhard

OS4User

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Re: OS/4 (technical details only)
« Reply #282 on: September 03, 2023, 02:43:03 pm »
now my system does not start anymore

Hi

Try some previous version.

Bernhard Pöttinger

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Re: OS/4 (technical details only)
« Reply #283 on: September 04, 2023, 01:38:16 pm »
now my system does not start anymore

Hi

Try some previous version.

Hi,
Version 6254 and Version 6256 do not work on my lenovo w520; the system does not boot. Version 6259 which is the last version is booting.

One thing is strange. I have 8GB memory; ca 3.5GB is available for OS/2; OS/4 kernel takes 1.2GB of 4Gb+ mem for swapping and emsFS takes 484MB. Why does emsFS not take the 2,8GB which are unused from 4GB+?

bernhard

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Re: OS/4 (technical details only)
« Reply #284 on: September 04, 2023, 01:58:30 pm »
Version 6259 which is the last version is booting.

Then everything is ok, HowTo is updated, pls check.

Why does emsFS not take the 2,8GB which are unused from 4GB+?

It could be emsFS restriction.