So is there a "relatively simple block device driver" I can use?
Even a howto would be useful. I understand how to get the NSS bit working
but linking with Linux is more of a challenge.
Thanks
Phil
-----Original Message-----
From: Arnd Bergmann [mailto:[EMAIL PROTECTED]
Sent: 23 September 2003 00:12
To: [EMAIL PROTECTED]
Subject: Re: Sharing /usr using VM
On Monday 22 September 2003 23:06, Richard Troth wrote:
> As one of my colleagues pointed out, this is a job for NSS!
> With an NSS-resident /usr, everyone would get it read-only.
> The "owner" Linux instance would define a new NSS when needed,
> fill it with current content, and then 'saveseg', at which point
> all in-use copies would go CLASS P and be purged upon release.
>
> Nifty, huh?
I guess you could even have writable copies for multiple guests
with VM taking care of copy-on-write behavior on a per-page
basis.
The biggest problems are that all the segments have to fit into
VM's main storage of 2GB and that linux needs to have a
'struct page' entry (~80 bytes in 2.6) in mem_map for each
addressable page, so each guest wastes 7MB of non-swappable
(inside linux) RAM for a /usr file system of 1GB.
Aside from that, it's the obvious solution and can be implemented
with a relatively simple block device driver.
Arnd <><
