Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz cpuid says: Intel Xeon E5-1600/E5-2600 v2 (Ivy Bridge-EP C1/M1/S1), 22nm ---- 8< ---- PV xpti=dom0=false,domu=true clocksource=xen -$ time strace -ce gettimeofday ./test2 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 100.00 73.935907 15 5000000 gettimeofday ------ ----------- ----------- --------- --------- ---------------- 100.00 73.935907 5000000 total real 6m22.827s user 1m36.107s sys 6m35.662s ---- 8< ---- PV xpti=dom0=false,domu=true clocksource=tsc -$ time strace -ce gettimeofday ./test2 real 0m0.186s user 0m0.100s sys 0m0.010s ---- 8< ---- PV xpti=dom0=false,domu=false clocksource=xen -$ time strace -ce gettimeofday ./test2 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 100.00 52.067931 10 5000000 gettimeofday ------ ----------- ----------- --------- --------- ---------------- 100.00 52.067931 5000000 total real 3m55.400s user 1m7.210s sys 3m45.235s ---- 8< ---- PV xpti=dom0=false,domu=false clocksource=tsc -$ time strace -ce gettimeofday ./test2 real 0m0.105s user 0m0.105s sys 0m0.000s ---- 8< ---- PVH pti clocksource=xen (no INVPCID) -$ time strace -ce gettimeofday ./test2 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 100.00 30.229025 6 5000000 gettimeofday ------ ----------- ----------- --------- --------- ---------------- 100.00 30.229025 5000000 total real 3m14.734s user 0m23.425s sys 2m23.567s ---- 8< ---- PVH nopti clocksource=xen -$ time strace -ce gettimeofday ./test2 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 100.00 8.854375 2 5000000 gettimeofday ------ ----------- ----------- --------- --------- ---------------- 100.00 8.854375 5000000 total real 0m49.933s user 0m3.959s sys 0m45.016s ---- 8< ---- PVH pti clocksource=tsc (no INVPCID) -$ time strace -ce gettimeofday ./test2 real 0m0.106s user 0m0.105s sys 0m0.000s ---- 8< ---- PVH nopti clocksource=tsc -$ time strace -ce gettimeofday ./test2 real 0m0.100s user 0m0.096s sys 0m0.004s ---- 8< ---- PVH nopti clocksource=tsc, after live migrate -$ time strace -ce gettimeofday ./test2 real 0m7.590s user 0m7.584s sys 0m0.002s