System clock jitter measure result. Using 8 vCpu SMP guest OS with using hypercall mark getting/leaving guest OS kernel state also the KVM path to boost the lock holder vCPU. The max jitter at run time is 6ms The two 200ms jitter below was from guest OS system initialization stage instead of run time clock jitter. ====================================================================== 11-> sysClkIntShow OSclock:0x80f8760 -- intrlen: 6804074 [ 1999 us] -- tickLen: 34020374 [ 9999 us] -- tickWin: 5103056 [ 1499 us] -- syncOff: 0 [ 0 us] -- timeerr: -17387492 [ -5.111 ms] [0.0004 %] [sync: -0.071 ms] -- intrerr: 0xffffffff99f36b1a [ -0.503 sec] [0.0404 %] +---------+--------------------+--------------------+-------------------------+ | ts | init | last | time [ms] | +---------+--------------------+--------------------+-------------------------+ | cpu_tsc | 0x000000031e754598 | 0x000003de99c1c6f8 | 1246665.096 | | vxticks | 0x00000000ffff1613 | 0x000000000000fd0d | 1246659.985 | +---------+--------------------+--------------------+-------------------------+ +---------+--------------------+--------------------+-------------------------+ | counter | count | time [ms] | delta [ms] [%] | +---------+--------------------+--------------------+---------------+---------+ | cpu_tsc | 4241201332576 | 1246665.096 | +0.000 | +0.0000 | | vxticks | 124666 | 1246659.985 | -5.111 | -0.0004 | | clk_obj | 124666 | 1246659.985 | +5.040 | +0.0004 | | clkintr | 623081 | 1246161.839 | -503.257 | -0.0404 | +---------+--------------------+--------------------+---------------+---------+ OSclock [0x80f8760] interrupt-source histogram -- clk freq: 500 Hz -- clk intr: 623082 +------+---------------------+----------------------------+ | pos# | Interval [ms] | clk ticks % | +------+---------------------+-------------------+--------+ | 0 | 0.000 .. 0.308 | 40 | 0.01 | | 1 | 0.308 .. 0.616 | 16 | 0.00 | | 2 | 0.616 .. 0.925 | 22 | 0.00 | | 3 | 0.925 .. 1.233 | 14 | 0.00 | | 4 | 1.233 .. 1.541 | 16 | 0.00 | | 5 | 1.541 .. 1.849 | 51 | 0.01 | | 6 | 1.849 .. 2.158 | 622769 | 99.95 | | 7 | 2.158 .. 2.466 | 43 | 0.01 | | 8 | 2.466 .. 2.774 | 13 | 0.00 | | 9 | 2.774 .. 3.082 | 13 | 0.00 | | 10 | 3.082 .. 3.390 | 17 | 0.00 | | 11 | 3.390 .. 3.699 | 11 | 0.00 | | 12 | 3.699 .. 4.007 | 4 | 0.00 | | 13 | 4.007 .. 4.315 | 5 | 0.00 | | 14 | 4.315 .. 4.623 | 3 | 0.00 | | 15 | 4.623 .. 4.932 | 2 | 0.00 | | 16 | 4.932 .. 5.240 | 1 | 0.00 | | 17 | 5.240 .. 5.548 | 5 | 0.00 | | 18 | 5.548 .. 5.856 | 26 | 0.00 | | 19 | 5.856 .. 6.164 | 8 | 0.00 | | 20 | 6.164 .. 6.473 | 2 | 0.00 | | 663 | 204.350 .. 204.658 | 1 | 0.00 | | 668 | 205.891 .. 206.199 | 1 | 0.00 | +------+---------------------+-------------------+--------+ | ---- | | 623083 | 100.00 | +------+---------------------+-------------------+--------+ System clock jitter measure result. Using 8 vCpu SMP guest OS without hypercall and the vanilla KVM PLE handler. The system clock jitter (run time) in guest OS coule be bigger than 400ms. ====================================================================== 11-> sysClkIntShow OSclock:0x8055760 -- intrlen: 6804067 [ 1999 us] -- tickLen: 34020337 [ 10000 us] -- tickWin: 5103050 [ 1499 us] -- syncOff: 0 [ 0 us] -- timeerr: -22314665 [ -6.559 ms] [0.0009 %] [sync: -0.032 ms] -- intrerr: 0xfffffffaca02d1f3 [ -6.579 sec] [0.9233 %] +---------+--------------------+--------------------+-------------------------+ | ts | init | last | time [ms] | +---------+--------------------+--------------------+-------------------------+ | cpu_tsc | 0x00000003359de5e8 | 0x000002379389f1d2 | 712496.568 | | vxticks | 0x00000000ffff160f | 0x0000000000002c60 | 712490.008 | +---------+--------------------+--------------------+-------------------------+ +---------+--------------------+--------------------+-------------------------+ | counter | count | time [ms] | delta [ms] [%] | +---------+--------------------+--------------------+---------------+---------+ | cpu_tsc | 2423937305578 | 712496.568 | +0.000 | +0.0000 | | vxticks | 71249 | 712490.008 | -6.559 | -0.0009 | | clk_obj | 71249 | 712490.008 | +6.527 | +0.0009 | | clkintr | 352959 | 705917.967 | -6578.601 | -0.9233 | +---------+--------------------+--------------------+---------------+---------+ OSclock [0x8055760] interrupt-source histogram -- clk freq: 500 Hz -- clk intr: 352959 +------+---------------------+----------------------------+ | pos# | Interval [ms] | clk ticks % | +------+---------------------+-------------------+--------+ | 0 | 0.000 .. 0.308 | 270 | 0.08 | | 1 | 0.308 .. 0.616 | 160 | 0.05 | | 2 | 0.616 .. 0.925 | 165 | 0.05 | | 3 | 0.925 .. 1.233 | 200 | 0.06 | | 4 | 1.233 .. 1.541 | 182 | 0.05 | | 5 | 1.541 .. 1.849 | 591 | 0.17 | | 6 | 1.849 .. 2.158 | 349872 | 99.13 | | 7 | 2.158 .. 2.466 | 530 | 0.15 | | 8 | 2.466 .. 2.774 | 151 | 0.04 | | 9 | 2.774 .. 3.082 | 123 | 0.03 | | 10 | 3.082 .. 3.390 | 87 | 0.02 | | 11 | 3.390 .. 3.699 | 65 | 0.02 | | 12 | 3.699 .. 4.007 | 53 | 0.02 | | 13 | 4.007 .. 4.315 | 38 | 0.01 | | 14 | 4.315 .. 4.623 | 27 | 0.01 | | 15 | 4.623 .. 4.932 | 34 | 0.01 | | 16 | 4.932 .. 5.240 | 44 | 0.01 | | 17 | 5.240 .. 5.548 | 24 | 0.01 | | 18 | 5.548 .. 5.856 | 37 | 0.01 | | 19 | 5.856 .. 6.164 | 32 | 0.01 | | 20 | 6.164 .. 6.473 | 22 | 0.01 | | 21 | 6.473 .. 6.781 | 30 | 0.01 | | 22 | 6.781 .. 7.089 | 21 | 0.01 | | 23 | 7.089 .. 7.397 | 12 | 0.00 | | 24 | 7.397 .. 7.706 | 17 | 0.00 | | 25 | 7.706 .. 8.014 | 13 | 0.00 | | 26 | 8.014 .. 8.322 | 3 | 0.00 | | 27 | 8.322 .. 8.630 | 9 | 0.00 | | 28 | 8.630 .. 8.938 | 7 | 0.00 | | 29 | 8.938 .. 9.247 | 7 | 0.00 | | 30 | 9.247 .. 9.555 | 3 | 0.00 | | 31 | 9.555 .. 9.863 | 2 | 0.00 | | 32 | 9.863 .. 10.171 | 8 | 0.00 | | 33 | 10.171 .. 10.479 | 6 | 0.00 | | 34 | 10.479 .. 10.788 | 1 | 0.00 | | 35 | 10.788 .. 11.096 | 3 | 0.00 | | 36 | 11.096 .. 11.404 | 6 | 0.00 | | 37 | 11.404 .. 11.712 | 1 | 0.00 | | 38 | 11.712 .. 12.021 | 1 | 0.00 | | 39 | 12.021 .. 12.329 | 2 | 0.00 | | 40 | 12.329 .. 12.637 | 2 | 0.00 | | 41 | 12.637 .. 12.945 | 3 | 0.00 | | 42 | 12.945 .. 13.253 | 4 | 0.00 | | 44 | 13.562 .. 13.870 | 2 | 0.00 | | 45 | 13.870 .. 14.178 | 3 | 0.00 | | 46 | 14.178 .. 14.486 | 2 | 0.00 | | 47 | 14.486 .. 14.795 | 5 | 0.00 | | 48 | 14.795 .. 15.103 | 3 | 0.00 | | 49 | 15.103 .. 15.411 | 1 | 0.00 | | 50 | 15.411 .. 15.719 | 2 | 0.00 | | 51 | 15.719 .. 16.027 | 3 | 0.00 | | 53 | 16.336 .. 16.644 | 2 | 0.00 | | 54 | 16.644 .. 16.952 | 2 | 0.00 | | 56 | 17.260 .. 17.569 | 2 | 0.00 | | 57 | 17.569 .. 17.877 | 1 | 0.00 | | 58 | 17.877 .. 18.185 | 1 | 0.00 | | 60 | 18.493 .. 18.801 | 1 | 0.00 | | 62 | 19.110 .. 19.418 | 1 | 0.00 | | 64 | 19.726 .. 20.034 | 1 | 0.00 | | 65 | 20.034 .. 20.343 | 1 | 0.00 | | 66 | 20.343 .. 20.651 | 1 | 0.00 | | 67 | 20.651 .. 20.959 | 1 | 0.00 | | 71 | 21.884 .. 22.192 | 2 | 0.00 | | 75 | 23.117 .. 23.425 | 1 | 0.00 | | 76 | 23.425 .. 23.733 | 1 | 0.00 | | 81 | 24.966 .. 25.274 | 2 | 0.00 | | 82 | 25.274 .. 25.582 | 1 | 0.00 | | 83 | 25.582 .. 25.891 | 3 | 0.00 | | 85 | 26.199 .. 26.507 | 1 | 0.00 | | 87 | 26.815 .. 27.123 | 1 | 0.00 | | 90 | 27.740 .. 28.048 | 1 | 0.00 | | 91 | 28.048 .. 28.356 | 2 | 0.00 | | 99 | 30.514 .. 30.822 | 1 | 0.00 | | 101 | 31.130 .. 31.438 | 1 | 0.00 | | 107 | 32.980 .. 33.288 | 1 | 0.00 | | 111 | 34.212 .. 34.521 | 1 | 0.00 | | 119 | 36.678 .. 36.986 | 1 | 0.00 | | 120 | 36.986 .. 37.295 | 1 | 0.00 | | 122 | 37.603 .. 37.911 | 1 | 0.00 | | 128 | 39.452 .. 39.760 | 1 | 0.00 | | 129 | 39.760 .. 40.069 | 1 | 0.00 | | 130 | 40.069 .. 40.377 | 1 | 0.00 | | 137 | 42.226 .. 42.534 | 1 | 0.00 | | 138 | 42.534 .. 42.843 | 1 | 0.00 | | 140 | 43.151 .. 43.459 | 1 | 0.00 | | 144 | 44.384 .. 44.692 | 1 | 0.00 | | 161 | 49.623 .. 49.932 | 1 | 0.00 | | 164 | 50.548 .. 50.856 | 1 | 0.00 | | 182 | 56.096 .. 56.404 | 1 | 0.00 | | 189 | 58.254 .. 58.562 | 1 | 0.00 | | 192 | 59.178 .. 59.487 | 1 | 0.00 | | 214 | 65.959 .. 66.267 | 1 | 0.00 | | 230 | 70.891 .. 71.199 | 1 | 0.00 | | 258 | 79.521 .. 79.829 | 1 | 0.00 | | 279 | 85.993 .. 86.302 | 1 | 0.00 | | 300 | 92.466 .. 92.774 | 1 | 0.00 | | 309 | 95.240 .. 95.548 | 1 | 0.00 | | 339 | 104.487 .. 104.795 | 1 | 0.00 | | 411 | 126.679 .. 126.987 | 1 | 0.00 | | 434 | 133.768 .. 134.076 | 1 | 0.00 | | 463 | 142.706 .. 143.014 | 1 | 0.00 | | 532 | 163.973 .. 164.281 | 1 | 0.00 | | 537 | 165.514 .. 165.823 | 1 | 0.00 | | 538 | 165.823 .. 166.131 | 1 | 0.00 | | 631 | 194.487 .. 194.795 | 1 | 0.00 | | 634 | 195.412 .. 195.720 | 1 | 0.00 | | 707 | 217.912 .. 218.220 | 1 | 0.00 | | 728 | 224.384 .. 224.693 | 1 | 0.00 | | 735 | 226.542 .. 226.850 | 1 | 0.00 | | 772 | 237.946 .. 238.254 | 1 | 0.00 | | 924 | 284.796 .. 285.104 | 1 | 0.00 | | 1346 | 414.865 .. 415.173 | 1 | 0.00 | | 1360 | 419.180 .. 419.488 | 1 | 0.00 | +------+---------------------+-------------------+--------+ | ---- | | 352959 | 100.00 | +------+---------------------+-------------------+--------+