xen-devel
Re: [Xen-devel] unnecessary VCPU migration happens again
On Dec 19, 2006, at 8:02, Xu, Anthony wrote:
Your patch is good, and reduce the majority of unnecessary migrations.
But the unnecessary migration still exist. I can still see about 5%
performance
degradation on above benchmark( KB and LTP).
In fact this patch had helped a lot (from 27% to 5%)
I can understand it is impossible to implement spreading VCPU over all
sockets/cores
and eliminate all unnecessary migration in the same time.
Is it possible for us to add a argument to function scheduler_init to
enable/disable
spreading VCPU feature?
I don't think this is a good idea. If you want to disable migration,
you can always
pin your VCPUs in place yourself using the cpu affinity masks.
If the attempt to balance work across sockets hurts performance of
reasonable
benchmarks, then perhaps it's still being too aggressive. right now,
such a
migration could happen on 10ms boundaries. i can try to smooth this
further.
Can you dump the credit scheduler stat counter before and after you run
the
benchmark? (^A^A^A on the dom0/hypervisor console to switch to the
hypervisor
and then type the "r" key to dump scheduler info). That along with an
idea of the
elapsed time between the two stat samples would be handy.
Cheers,
Emmanuel.
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