Re: Expand VM

From: User & (
Date: Thu Jan 23 2003 - 14:40:14 EST

Hi Valdis

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


On Thu, 23 Jan 2003 11:55:38 -0500, Valdis.Kletnieks wrote
> On Thu, 23 Jan 2003 12:56:27 -0300, User &
> <> said:
> > 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 ,
> > 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.
> > But i donīt 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
> > 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 nasty dragons in this.
> You're probably better off buying more RAM and disk for your A machine.
> --
> Valdis Kletnieks
> Computer Systems Senior Engineer
> Virginia Tech


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