Expand VM

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Post by User & » Fri, 24 Jan 2003 18:00:26



Hi all

I have one idea , and this is about expand virtual memory on linux boxes
connected in LAN.
Example: Linux A is processing come information , and need more memory , so
with this source , Linux A could access virtual memory on Linux B in LAN.
But i dont know how translate the virtual address between Linux A and B , to
have success in acess VM, or how to send all the process for Linux B to be
processed.

Any ideas ?

Thanks
Breno

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Post by Richard B. Johnso » Fri, 24 Jan 2003 18:10:07



> Hi all

> I have one idea , and this is about expand virtual memory on linux boxes
> connected in LAN.
> Example: Linux A is processing come information , and need more memory , so
> with this source , Linux A could access virtual memory on Linux B in LAN.
> But i dont know how translate the virtual address between Linux A and B , to
> have success in acess VM, or how to send all the process for Linux B to be
> processed.

> Any ideas ?

> Thanks
> Breno

Use a swap-file on another machine on the LAN to extend your virtual
memory if you run out of local swap-file space.

Cheers,
* Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

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Post by John Bradfor » Fri, 24 Jan 2003 18:30:11


Quote:> Use a swap-file on another machine on the LAN to extend your virtual
> memory if you run out of local swap-file space.

What would be really good would be a multiple gigabyte solid state
'disk', on a shared SCSI bus...

John.
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Post by Sean Neakum » Fri, 24 Jan 2003 18:40:10


commence  John Bradford quotation:

Quote:>> Use a swap-file on another machine on the LAN to extend your
>> virtual memory if you run out of local swap-file space.

> What would be really good would be a multiple gigabyte solid state
> 'disk', on a shared SCSI bus...

If you can afford gigabytes of solid state memory, you can surely
afford to properly fit your boxes out in the first place.

--
 /                          |
[|] Sean Neakums            | Size *does* matter.

 \                          |
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Post by John Bradfor » Fri, 24 Jan 2003 19:00:22


Quote:> >> Use a swap-file on another machine on the LAN to extend your
> >> virtual memory if you run out of local swap-file space.

> > What would be really good would be a multiple gigabyte solid state
> > 'disk', on a shared SCSI bus...

> If you can afford gigabytes of solid state memory, you can surely
> afford to properly fit your boxes out in the first place.

Good point :-)

What I'd really like to see is a single device which appears as two
logical IDE or SCSI devices, one of which has 512 Mb of battery backed
RAM, and the other one 512 Mb of EEPROM.

No need for expensive flash memory, just cheap DRAM, and a few NiMH
cells to keep the RAM contents intact when the main power was
disconnected.

I've seen loads of solid state devices based on flash memory, but few
that are based on battery backed DRAM :-(.

John.
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Post by Valdis.Kletni.. » Fri, 24 Jan 2003 19:00:22



Quote:> I have one idea , and this is about expand virtual memory on linux boxes
> connected in LAN.
> Example: Linux A is processing come information , and need more memory , so
> with this source , Linux A could access virtual memory on Linux B in LAN.

We've seen *this* done before (remember diskless Sun3-50's?) - the /dev/swap
file would be a large file on an NFS mount from a server.  At the time, this
actually made performance sense, because the old 'Shoebox' drives the -50
came with were incredibly slow, and you could actually do an NFS operation
to a larger server (a -280 with Fujitsu SuperEagle disks, for instance) faster
than talking to the local disk.

These days, it's probably easier and cheaper to just buy more RAM and/or disk
for Linux A.

Quote:> But i dont know how translate the virtual address between Linux A and B , to
> have success in acess VM, or how to send all the process for Linux B to be
> processed.

Sending the whole process to Linux B to be processed is called "process
migration", and is a difficult problem.  Moving the memory image of the
process is usually pretty easy.  What is difficult is moving things like
references to open files, file locks, and so on (what if the process is
actively writing to block 739 of /usr/foo/some.file, and the LinuxB machine
doesn't have a /usr/foo, or the permissions on some.file don't match, or
another process has it locked, or... ) There be * dragons in this.

You're probably better off buying more RAM and disk for your A machine.
--
                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                *ia Tech

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Post by kkon.. » Fri, 24 Jan 2003 19:20:05


Quote:> I have one idea , and this is about expand virtual memory on linux boxes
> connected in LAN.
...
> Any ideas ?

try SCI ? -- eg., http://sci-serv.inrialpes.fr/

kenji
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Post by Herman Oosthuyse » Fri, 24 Jan 2003 20:00:23


There is a good reason for that: Power consumption.

A large SDRAM disk would require refresh logic etc.  So you will end up
with something closely resembling bad notebook PC.


> I've seen loads of solid state devices based on flash memory, but few
> that are based on battery backed DRAM :-(.

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Post by John Bradfor » Fri, 24 Jan 2003 20:50:09


Quote:> > I've seen loads of solid state devices based on flash memory, but few
> > that are based on battery backed DRAM :-(.
> There is a good reason for that: Power consumption.

> A large SDRAM disk would require refresh logic etc.  So you will end up
> with something closely resembling bad notebook PC.

I suppose it makes sense for portable devices, but would it really be
that bad for desktop/server use?  I was only thinking of about a 24
hour battery backup time - to keep the contents overnight, for
example.

John.
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Post by Herman Oosthuyse » Fri, 24 Jan 2003 21:50:06


The trouble is that you will spend so much money on the power supply,
that the product won't make economic sense.  It would be better to just
use a general purpose PC mother board, PSU and a UPS, since then, you
get tremendous economy of scale.


>>>I've seen loads of solid state devices based on flash memory, but few
>>>that are based on battery backed DRAM :-(.

>>There is a good reason for that: Power consumption.

>>A large SDRAM disk would require refresh logic etc.  So you will end up
>>with something closely resembling bad notebook PC.

> I suppose it makes sense for portable devices, but would it really be
> that bad for desktop/server use?  I was only thinking of about a 24
> hour battery backup time - to keep the contents overnight, for
> example.

> John.

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Post by Valdis.Kletni.. » Fri, 24 Jan 2003 22:10:12


On Thu, 23 Jan 2003 16:40:14 -0300, User & said:

Quote:> Create a new VMA on Linux B for Linux A is easy , but i have a problem , the
> address of VMA is returned on Linux B , so the VMA created on Linux B can not
> be used for process of linux A.

It's unclear whether you're just trying to use B for added swap space, or
if you want B to actually run code.

If it's the former, all you have to do is allocate a lot of disk space on B,
and NFS export it to A, and then have A mount it (you might need to
use a loopback mount of a file on the NFS partition and then 'swapon' the
loopback - I dont think swapon will directly take an NFS file)

Quote:> The problem is "how can i return address of VMA created on LINUX B to Linux
> A , and use this space ?".

If you're trying to get B to actually run code, it gets a lot more messy, as
you have to worry about open file descriptors, race conditions, and many
other things.
--
                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                *ia Tech

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Post by Bill Davidse » Sat, 25 Jan 2003 17:30:15



> I have one idea , and this is about expand virtual memory on linux boxes
> connected in LAN.
> Example: Linux A is processing come information , and need more memory , so
> with this source , Linux A could access virtual memory on Linux B in LAN.
> But i dont know how translate the virtual address between Linux A and B , to
> have success in acess VM, or how to send all the process for Linux B to be
> processed.

> Any ideas ?

1 - NFS mount a big file and use that from swap space
2 - you could try the network block device stuff, at one time I believe I
had that working with RAID-1

--

  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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Post by Patrizio Brun » Wed, 29 Jan 2003 08:00:13


http://www.openmosix.org


> Hi all

> I have one idea , and this is about expand virtual memory on linux boxes
> connected in LAN.
> Example: Linux A is processing come information , and need more memory , so
> with this source , Linux A could access virtual memory on Linux B in LAN.
> But i dont know how translate the virtual address between Linux A and B , to
> have success in acess VM, or how to send all the process for Linux B to be
> processed.

> Any ideas ?

> Thanks
> Breno

> ----------------------
> WebMail Bandnet.com.br

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1. Looking for VMS Patch and VMS ARC

Howdy,

I'm in need of a VMS versions of PATCH and ARC.  We use them
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I've got sources to both the UNIX ARC program and UNIX PATCH, but
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Well, am I in luck or not?  If you have any leads, I'd love to hear

"...!tektronix!vice!budda!glennl".

                        Thanks,

                        Glenn

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