big latency while under HV

[Ivan Krivonos]

Hi,

i`m working on the embedded hypervisor targeting QorIQ platforms (p3041/p4080).
I have working prototype starting custom RTOS on just single core in the guest
space. What I see is the big latency (up to 3 times more) in RTOS running atop
of HV comparing to RTOS running bare-metal. I`m using lmbench utility.
It shows

nteger mul: 3.48 nanoseconds
integer div: 30.44 nanoseconds
integer mod: 13.92 nanoseconds
int64 bit: 1.75 nanoseconds
int64 add: 1.42 nanoseconds
int64 mul: 6.95 nanoseconds
HV:hvpriv_count 60000
int64 div: 447.56 nanoseconds
int64 mod: 385.42 nanoseconds
float add: 7.12 nanoseconds
float mul: 6.95 nanoseconds
float div: 33.05 nanoseconds
double add: 7.11 nanoseconds
double mul: 8.70 nanoseconds
double div: 57.36 nanoseconds
float bogomflops: 46.98 nanoseconds
double bogomflops: 73.09 nanoseconds

The bare-metal results are 3x better. Does anybody have any ideas on what
may be the source of such latency ? I forward all the exceptions to
the guest w/o
affecting HV. Only hvpriv is processed, it takes not more than 2 bus cycles.
Sorry for poor english