Virtualbox guest responding really slow over SSH, VBoxHeadLess stuck in 99.9% system time

I've been using Vagrant/virtualbox on a relatively new laptop with decent specs (16GB memory, Intel i7 4710HQ cpu, dual m-sata SSD).

So far, with every guest I run, I encounter really high latency, where keystrokes over SSH are echoed seconds later. (I did take check the usual SSH connection issues with reverse DNS lookup and GSSAPI auth, they do not apply and would only affect the initial connection.)

Meanwhile (and at other random times) one core will spin up to 100% utilisation, which is all spent by VBoxHeadLess inside select().

$ ps -o time -p  5257; time sudo strace -c -p 5257 ; ps -o time -p  5257
TIME         
00:23:51
Process 5257 attached
^CProcess 5257 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 99.95    3.214696      128588        25           select
  0.03    0.000822          29        28           read
  0.02    0.000521          23        23           futex
  0.01    0.000413          21        20           sched_yield
------ ----------- ----------- --------- --------- ----------------
100.00    3.216452                    96           total

real    0m3.81s
user    0m0.00s
sys     0m0.01s
    TIME
00:23:55

$ ps -fp  5257
UID        PID  PPID  C STIME TTY TIME     CMD
henk      5257 25788 45 16:34 ?   00:18:20 /usr/lib/virtualbox/VBoxHeadless

Note the ps -o time ouput before and after

00:23:51
00:23:55

Combined with the time ... result of 3.81s., this confirms that the process is actually spending all of its time in the kernel, just waiting for events.

Meanwhile, the host kernel appears to be spinning on a lock in order to resolve that select().

I've used virtualbox/vagrant on a more modest i5 laptop, with the same ubuntu 14.04, and never saw this kind of behaviour.

Questions:

1. How can I dig deeper to find out the cause of the excessive cpu wasted here?


2. Is anyone familiar with similarly slow responding virtualbox guests?