The patch I referenced (and forgot to attach) is located here:
http://www.silby.com/tsc.c-no_vm_smp_tsc.patch
Thanks to those who pointed out my error to me. :)
Mike Silby Silbersack
On Tue, 16 Aug 2011, Mike Silbersack wrote:
Hi all,
Thanks to a lightning strike, I recently upgraded my ESXi 4.1 system from an
old Athlon X2 to a shiny new Core i5-2500K. I order to see how fast it was,
I decided to run some buildworlds. I tried my FreeBSD 9 based VM first, and
was unhappy with what I saw - many mpt timeouts were reported, and the
filesystem ended up requiring a lot of fscking. My FreeBSD 8 based VM, on
the other hand, was quite happy.
After some trial and error, I determined that using the TSC as a timecounter
with the VM in SMP mode was the root cause. If I switch the VM to one vCPU
and run with the TSC, the buildworld runs fine. If I leave it with two vCPUs
and change the timecounter to ACPI, then it runs fine too. Based on these
results, I created the attached patch; it turns the priority of the TSC down
to -100 if it determines that it is running inside a virtualized SMP
environment. (I did not do testing on KVM or qemu, but I am assuming that
they probably do not have TSC emulation perfect either.)
I'd like to get this into 9.0 so that it works reliably for people who run it
in a virtual environment on modern hardware. If someone could code review
the patch, I would greatly appreciate it.
Thanks,
Mike Silby Silbersack
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