I have been building with SKAS4 (host and guest) and was trying to increase the amount of memory to an instance. According the Jeff's book, I should be able to do the following:

uml_mconsole test config mem=+32m

However, when I try this it has no apparent effect. 'config mem' shows now difference before and after 'config mem=+32m', nothing is printed to dmesg, no change is apparent in a call to 'free -tm' in the guest.

The guest does report that MADV_REMOVE support is okay. Any idea what is missing? Here is the complete kernel startup messages:

vineladm@gallardo:/vinel/tmp$ /vinel/src/build/guest/linux- mem=32m ubd0=ubuntu_804lts.img
Core dump limits :
soft - 0
hard - NONE
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...missing
Checking for tmpfs mount on /dev/shm...OK
Checking PROT_EXEC mmap in /dev/shm/...OK
Checking for SKAS4 support in the host:
/proc/self/mm ... OK
new_mm ... OK
switching over ... switched back ... OK
Full CPU fault information in siginfo_t ... OK
Full CPU fault information in PTRACE_GETSIGINFO ... OK
vcpu ... OK
UML running in SKAS4 mode
Linux version (vineladm@gallardo) (gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu3)) #1 Tue Dec 9 16:13:20 NZDT 2008
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 8080
Kernel command line: mem=32m ubd0=ubuntu_804lts.img root=98:0
PID hash table entries: 128 (order: 7, 1024 bytes)
Dentry cache hash table entries: 4096 (order: 3, 32768 bytes)
Inode-cache hash table entries: 2048 (order: 2, 16384 bytes)
Memory: 28984k available
Mount-cache hash table entries: 256
Checking that host ptys support output SIGIO...Yes
Checking that host ptys support SIGIO on close...No, enabling workaround
net_namespace: 280 bytes
Using 2.6 host AIO
NET: Registered protocol family 16
NET: Registered protocol family 2
IP route cache hash table entries: 512 (order: 0, 4096 bytes)
TCP established hash table entries: 1024 (order: 2, 16384 bytes)
TCP bind hash table entries: 1024 (order: 1, 8192 bytes)
TCP: Hash tables configured (established 1024 bind 1024)
TCP reno registered
mconsole (version 2) initialized on /home/vineladm/.uml/3QIrGu/mconsole
Checking host MADV_REMOVE support...OK
VFS: Disk quotas dquot_6.5.1
Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
io scheduler noop registered
io scheduler anticipatory registered (default)
io scheduler deadline registered
io scheduler cfq registered
TCP cubic registered
NET: Registered protocol family 1
NET: Registered protocol family 17
Initialized stdio console driver
Console initialized on /dev/tty0
console [tty0] enabled
Initializing software serial port version 1
console [mc-1] enabled
 ubda: unknown partition table
kjournald starting.  Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
VFS: Mounted root (ext3 filesystem) readonly.
 * Setting preliminary keymap...                                                Couldnt get a file descriptor referring to the console
Couldnt get a file descriptor referring to the console
Couldnt get a file descriptor referring to the console
 * Starting basic networking...                                          [ OK ] 
 * Starting kernel event manager...                                      [ OK ] 
 * Loading hardware drivers...                                           [ OK ] 
 * Loading kernel modules...                                                     * Loading manual drivers...                                             [ OK ] 
 * Setting kernel variables...                                           [ OK ] 
 * Activating swap...                                                    [ OK ] 
 * Checking file systems...                                                     fsck 1.40.8 (13-Mar-2008)
                                                                         [ OK ]
 * Mounting local filesystems...                                         [ OK ] 
 * Activating swapfile swap...                                           [ OK ] 
 * Checking minimum space in /tmp...                                     [ OK ] 
 * Skipping firewall: ufw (not enabled)...                               [ OK ] 
 * Configuring network interfaces...                                     [ OK ] 
 * Starting system log daemon...                                         [ OK ] 
 * Starting kernel log daemon...                                         [ OK ] 
 * Starting deferred execution scheduler atd                             [ OK ] 
 * Starting periodic command scheduler crond                             [ OK ] 
 * Running local boot scripts (/etc/rc.local)                            [ OK ] 
Unable to find swap-space signature

Cameron Kerr <ckerr@cs.otago.ac.nz>
Teaching Fellow, Computer Science, University of Otago