Avi Kivity wrote: > Anthony Liguori wrote: >> Avi Kivity wrote: >>> Anthony Liguori wrote: >>>> Avi Kivity wrote: >>>>> Anthony Liguori wrote: >>>>>> It's pretty erratic. If I run if a few times at any rate, >>>>>> sometimes I get 0.0 and sometimes I get a more sane result. >>>>> >>>>> I expect the newer kernel is sometimes disqualifying the timestamp >>>>> counter from being used as a clocksource. Running pinned to a >>>>> cpu may improve things. >>>> >>>> Things get better if I disable the PM timer and if I pin to a >>>> single CPU. >>>> >>> >>> Can you post the magic command line for future reference? >> >> I disabled CONFIG_X86_PM_TIMER in the kernel config and then used: >> >> sudo taskset 1 qemu -hda /dev/volumes/kvm-dev -m 2000 -vnc :3 >> -kernel /build/kvm/arch/i386/boot/bzImage -append "root=0301 ro" >> > > Ah, there's probably a kernel command line to select the clock without > resorting to config options. Somebody probably wrote a book about it. > >> However, this doesn't appear to be a perfect solution. If I launch >> the VM redirecting everything to the serial port, I again start >> having problems with virtbench. I guess the shear rate of interrupts >> using the serial port throws off the accuracy of the clock? > > I'd have guessed that there wouldn't be many writes to the serial port > when testing is in progress.
It's less stable then I thought. You were right btw, the guest is deciding the TSC is too unreliable. It happens every once and while (although the taskset/no pm timer combination helps a whole lot). Regards, Anthony Liguori ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
