Re: [kvm-devel] performance with guests running 2.4 kernels (specifically RHEL3)

[Avi K. <av...@qu...>]

David S. Ahern wrote:
> That does the trick with kscand.
>
>   

Not so fast...  the patch updates the flood count to 5.  Can you check 
if a lower value still works?  Also, whether updating the flood count to 
5 (without the rest of the patch) works?

Unconditionally bumping the flood count to 5 will likely cause a 
performance regression on other guests.

While I was able to see excessive flooding, I couldn't reproduce your 
kscand problem.  Running /bin/true always returned immediately for me.

> Do you have recommendations for clock source settings? For example in my
> test case for this patch the guest gained 73 seconds (ahead of real
> time) after only 3 hours, 5 min of uptime.
>   

The kernel is trying to correlate tsc and pit, which isn't going to work.

Try disabling the tsc, set edx.bit4=0 for cpuid.eax=1 in qemu-kvm-x86  
.c do_cpuid_ent().

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error compiling committee.c: too many arguments to function