Luca Tettamanti wrote: > Il Wed, Aug 22, 2007 at 08:02:07AM +0300, Avi Kivity ha scritto: > >> Luca Tettamanti wrote: >> >> >>> Actually I'm having troubles with cyclesoak (probably it's calibration), >>> numbers are not very stable across multiple runs... >>> >>> >> I've had good results with cyclesoak; maybe you need to run it in >> runlevel 3 so the load generated by moving the mouse or breathing >> doesn't affect meaurements. >> > > This is what I did, I tested with -no-grapich in text console. > >
Okay. Maybe cpu frequency scaling confused it then. Or something else? >>> The guest is an idle kernel with HZ=1000. >>> >>> >> Can you double check this? The dyntick results show that this is either >> a 100Hz kernel, or that there is a serious bug in dynticks. >> > > Ops I sent the wrong files, sorry. > > This is QEMU, with dynticks and HPET: > > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 52.10 0.002966 0 96840 clock_gettime > 19.50 0.001110 0 37050 timer_gettime > 10.66 0.000607 0 20086 timer_settime > 10.40 0.000592 0 8985 2539 sigreturn > 4.94 0.000281 0 8361 2485 select > 2.41 0.000137 0 8362 gettimeofday > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.005693 179684 5024 total > This looks like 250 Hz? And a huge number of settime calls? Something's broken with dynticks. > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 93.37 0.025541 3 10194 10193 select > 4.82 0.001319 0 33259 clock_gettime > 1.10 0.000301 0 10195 gettimeofday > 0.71 0.000195 0 10196 10194 sigreturn > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.027356 63844 20387 total > This is expected and sane. > And this KVM: > > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 42.66 0.002885 0 45527 24 ioctl > 25.62 0.001733 0 89305 clock_gettime > 13.12 0.000887 0 34894 timer_gettime > 7.97 0.000539 0 18016 timer_settime > 4.70 0.000318 0 12224 7270 rt_sigtimedwait > 2.79 0.000189 0 7271 select > 1.86 0.000126 0 7271 gettimeofday > 1.27 0.000086 0 4954 rt_sigaction > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.006763 219462 7294 total > Similarly broken. The effective frequency is twice qemu's. I think we had the same effect last time. > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 49.41 0.004606 0 59900 27 ioctl > 24.14 0.002250 0 31252 21082 rt_sigtimedwait > 9.65 0.000900 0 51856 clock_gettime > 8.44 0.000787 0 17819 select > 4.42 0.000412 0 17819 gettimeofday > 3.94 0.000367 0 10170 rt_sigaction > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.009322 188816 21109 total > > Similarly sane. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.
