[Users] prlctl is sensibly slower than vzctl

[Jean Weisbuch]

On OpenVZ 7 servers, using prlctl is sensibly slower than using the 
similar command with vzctl/vzlist.


For example, on a server with 28 running containers, it takes always 
around 0.9seconds to do a "prlctl list" while it takes less than 0.02s 
to do a "vzlist".

Doing a "prlctl/vzctl exec /bin/echo" takes 0.2s with prlctl and 0.02s 
with vzctl on the same container.


Using strace, the top 5 syscalls by time elapsed with "prlctl exec" :

    0.05user 0.04system 0:00.24elapsed 41%CPU (0avgtext+0avgdata
    16084maxresident)k
    0inputs+0outputs (0major+4202minor)pagefaults 0swaps
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
      25.47    0.049546         300       165        11 futex
      22.68    0.044114        1225        36           poll
      22.49    0.043752       43752         1           wait4
      15.16    0.029495         301        98         2 read
       7.99    0.015546         273        57           ppoll


Same with "vzctl exec" :

    0.00user 0.01system 0:00.03elapsed 59%CPU (0avgtext+0avgdata
    3568maxresident)k
    0inputs+0outputs (0major+1696minor)pagefaults 0swaps
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
      72.76    0.020719        6906         3           wait4
       4.46    0.001270           9       149           mmap
       3.90    0.001111          10       111        10 open
       3.60    0.001025           8       128           write
       3.21    0.000913          11        84           read



I have the same issue on every OpenVZ 7 servers i tested with vzctl 
"v.7.0.188-1.vz7", prlctl "7.0.153" and a "3.10.0-862.11.6.vz7.64.7" kernel.

Is it a known bug or limitation? should i fill a bug report about it?