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

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

On Mon, 27 Mar 2006, Christopher S. Aker wrote:

> David Lang wrote:
>> what could I do to assist in tracking down what is causing the contention?
>
> Are you running a skas3-patched host kernel?  You didn't mention if you were 
> running in 32bit mode.  I don't believe there's a skas patch for 64bit 
> kernels (yet).  IMO, skas3 is required what you're after.
>
> 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)

>> I upped the pid_max value to 128000 to give me some headroom there (each
>> of the first 18 uml instances will end up running ~3600 processes when
>> they finish booting)
>
> 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.

> The other two things are:
>
> Use the cfq disk scheduler.  elevator=cfq on your kernel command line will do 
> that, as long as it's compiled into your host's kernel.
>
> 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

ls -ls shows
305356 -rw-rw-rw-  1 root  root  1073741825 2006-03-24 18:15 root_fs.basebuild2
   9580 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1a-b
  14880 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1a-p
  12632 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1b-b
   5512 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1b-p
   5584 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1c-b
  12180 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1c-p
  14716 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1d-b
  16164 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1d-p
  12916 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1e-b
   9504 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:13 root_fs.methane1e-p
  10896 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 12:19 root_fs.methane1z-b
   5780 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane1z-p
   6516 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 15:36 root_fs.methane2a-p
   7980 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:14 root_fs.methane2b-p
   6056 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 15:36 root_fs.methane2c-p
   5968 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 15:36 root_fs.methane2d-p
   7704 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.methane2e-p
   7640 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:14 root_fs.methane2z-p
  19364 -rw-rw-rw-  1 dlang staff 1074016257 2006-03-27 17:15 root_fs.router


the command line to start these is

./linux-2.6.16-32 umid=methane1a-p ubd=memmap ubd0=root_fs.methane1a-p,root_fs.basebuild2 con0=tty:/dev/con-m1ap con=pty ssl=pty eth0=tuntap,m1ap-e0 eth1=tuntap,m1ap-e1 eth2=tuntap,m1ap-e2 eth3=tuntap,m1ap-e3 mem=400m stderr=1 </dev/con-m1ap >/dev/con-m1ap 2>/dev/con-m1ap &

David Lang