Re: [uml-user] what are the current limits on how many uml's on one host?

[David L. <da...@la...>]

On Tue, 28 Mar 2006, Blaisorblade wrote:

>>> http://www.user-mode-linux.org/~blaisorblade/patches/skas3-2.6/
>
>> sorry, the host is a dual Opteron 252 with 8G of ram running 2.6.16 (which
>> I understood included the skas patch)
>
> No, it doesn't if you don't patch it. Add the patch, but you can't run them in
> full SKAS3; you can pass "mode=skas0" to force skas0 mode, but you can then
> also pass "noprocmm" to force half SKAS3.

Ok, I've gone through and read the docs on blaisorblade's pages about 
SKAS, and I'm still not understanding things.

the 2.6.16 kernel includes a SKAS option in the configs (it only shows if 
you have TT mode enabled)

when they boot up the uml's report that they are starting in skas0 mode

however, the discussions you have up don't seem to match the bahavior of 
the resulting system (the discussions talk about TT vs SKAS mode, is this 
TT vs SKAS3 mode?)

it sounds as if I need to apply the SKAS patches and then pass "noprocmm" 
to get the 'half SKAS3' mode

is this correct?

>>> Sounds to me like you're running those UMLs in TT mode.  If you
>>> can't/aren't going to patch your host with skas3, at least run a recent
>>> 2.6-um kernel in skas0 mode, which doesn't require a host kernel patch.
>
>> they are running in skas mode, staticly compiled. the um's are 32-bit
>> 2.6.16 TT mode disabled to enable static linking. the systems finish the
>> boot sequence after useing about 12 min of cpu time each.
>
>>> Use tmpfs mount for TMPDIR, as UML will use that to store its memory
>>> file.
>
>> very little disk activity is takeing place during this time these are all
>> COW root images from a ~300M base image
>
> He's talking about UML's ram, not about disk images - that's mmapped from a
> file in $TMPDIR (normally /tmp).

Ok, I'll define $TMPDIR to be /dev/shm (which debian mounts a tmpfs on) 
and try this again

David Lang