I'm not sure if this is a UML issue, but my machine is acting very
strange, so I'm wondering if it is.

I have a guest that has 512Mb of memory assigned to it.  After running
mysql, apache, and mongrel (ruby on rails application server) for
several days, the machine has killed off mysql and mongrel (as well as
several apache children) because it is running out of ram.  Usage of the
command "free -m" confirms that this is the case:

             total       used       free     shared    buffers
cached
Mem:           499        495          3          0          0
5
-/+ buffers/cache:        489         10
Swap:         1907          2       1904

Usage of top, however, shows that there isn't any process using anywhere
near that kind of RAM (see the end of the message for top output).

I am confused as to what is going on.  Could the UML kernel be leaking
memory?  Is it possible my machine got rooted (running ubuntu gutsy and
stay up to date on security updates so that seems unlikely)?

For reference, I am running a vanilla Ubuntu gutsy server install on the
host, and kernel version 2.6.23 on the guest (precompiled kernel
downloaded from uml.nagafix.co.uk).  The guest is also running a vanilla
ubuntu gutsy server install.

I hope you can provide some advice as to more diagnostics to run.  I
have rebooted the machine, but this is the second time this has
happened, so I think it will happen again.  Note that the guest would
not restart with a "shutdown -r now" command and instead hung with the
terminal output "Deactivating swap..."  I had to kill off the guest from
the host and restart.  Note also that this host runs many other guests
off the same kernel (although this is the only one running mongrel) and
I haven't seen this behavior on any of them except this one.

Jonas



It should be mentioned that although this top output does not show it,
there were two zombie processes present (mysqd and logger) that were
both children of mysql-safe until I killed mysql-safe to see if the
memory would come back.

top - 12:51:18 up 19 days, 19:18,  2 users,  load average: 0.00, 0.00,
0.03
Tasks:  28 total,   1 running,  27 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,
0.0%st
Mem:    511248k total,   507600k used,     3648k free,      636k buffers
Swap:  1953116k total,     2804k used,  1950312k free,     6132k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+
COMMAND                                                                         
                                                                                
                
    1 root      20   0  2284  116   68 S  0.0  0.0   0:00.13
init                                                                            
                                                                                
                
    2 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
kthreadd                                                                        
                                                                                
                
    3 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
ksoftirqd/0                                                                     
                                                                                
                
    4 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00
watchdog/0                                                                      
                                                                                
                
    5 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
events/0                                                                        
                                                                                
                
    6 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
khelper                                                                         
                                                                                
                
   40 root      15  -5     0    0    0 S  0.0  0.0   0:00.16
kblockd/0                                                                       
                                                                                
                
   42 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
cqueue/0                                                                        
                                                                                
                
   62 root      15  -5     0    0    0 S  0.0  0.0   0:06.91
kswapd0                                                                         
                                                                                
                
  111 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
aio/0                                                                           
                                                                                
                
  125 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
cifsoplockd                                                                     
                                                                                
                
  126 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
cifsdnotifyd                                                                    
                                                                                
                
  136 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
cryptd                                                                          
                                                                                
                
  708 root      15  -5     0    0    0 S  0.0  0.0   0:00.00
rpciod/0                                                                        
                                                                                
                
  797 root      15  -5     0    0    0 S  0.0  0.0   0:02.61
kjournald                                                                       
                                                                                
                
  916 root      16  -4  2316    4    0 S  0.0  0.0   0:00.19
udevd                                                                           
                                                                                
                
  919 root      20   0  2044    4    0 S  0.0  0.0   0:00.02
udevmonitor                                                                     
                                                                                
                
 1299 root      18  -2  2316    4    0 S  0.0  0.0   0:00.01
udevd                                                                           
                                                                                
                
 1961 root      20   0  1692    4    0 S  0.0  0.0   0:00.00
getty                                                                           
                                                                                
                
 2037 root      20   0  5280  260  168 S  0.0  0.1   0:00.37
sshd                                                                            
                                                                                
                
 2540 root      20   0  1692    4    0 S  0.0  0.0   0:00.00
getty                                                                           
                                                                                
                
 3159 root      20   0  3548  192  124 S  0.0  0.0   0:00.74
cron                                                                            
                                                                                
                
23749 root      20   0     0    0    0 S  0.0  0.0   0:00.00
pdflush                                                                         
                                                                                
                
23872 root      20   0     0    0    0 S  0.0  0.0   0:00.00
pdflush                                                                         
                                                                                
                
23904 root      20   0  8032 1524 1144 S  0.0  0.3   0:00.01
sshd                                                                            
                                                                                
                
23906 jmeyer    20   0  8180 1324  880 S  0.0  0.3   0:00.06
sshd                                                                            
                                                                                
                
23907 jmeyer    20   0  5808 2416 1360 S  0.0  0.5   0:00.12
bash                                                                            
                                                                                
                
24093 jmeyer    20   0  2364 1104  876 R  0.0  0.2   0:00.00 top


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