top seems to report wrong CPU usage (HVMPV)

[Hugo Silva]

Hello,


89 processes:  4 running, 71 sleeping, 14 waiting
CPU: 77.1% user,  0.0% nice, 21.1% system,  1.8% interrupt,  0.0% idle
Mem: 151M Active, 194M Inact, 96M Wired, 3508K Cache, 60M Buf, 41M Free
Swap: 512M Total, 596K Used, 511M Free

   PID USERNAME PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
82983   2002    77    0   115M   103M RUN      0:02 15.97% cc1plus
    13 root      -8    -     0K    48K -        2:20  0.98% geom{g_down}
    11 root     155 ki31     0K    16K RUN     19.7H  0.00% idle
    12 root     -60    -     0K   224K WAIT     1:12  0.00% intr{swi4: 
clock}


When running virtualized (hvm+pv, haven't really tried just hvm) I keep 
noticing that there's a huge discrepancy between the %cpu top claims a 
process is using vs the total cpu% being used.

In the above example, that is the view from a FreeBSD 9.0-rel-p1 hvm+pv 
amd64 jailhost (cc1plus is running in a jail); -SH was given to top.

 From inside the jail, we see:

CPU: 90.8% user,  0.0% nice,  9.2% system,  0.0% interrupt,  0.0% idle
Mem: 154M Active, 187M Inact, 100M Wired, 8568K Cache, 60M Buf, 36M Free
Swap: 512M Total, 596K Used, 511M Free

   PID USERNAME PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
83454 <cut>    78    0   118M   106M RUN      0:02 19.97% cc1plus


There is a *huge* discrepancy.

I'm not sure what could be the cause. If it helps, the dom0 is running 
Xen 3.3.2 on NetBSD -current.

Is anyone else seeing similar behavior from the system?


Thanks,

Hugo