Re: [Xen-devel] unnecessary VCPU migration happens again

[Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>]

Hi Anthony.

Based on the number of "ticks" on CPU0 that occurred between the
two stat dumps, over 16 minutes elapsed during that time.

During that time, 364 regular migrations occurred. These are migrations
that happen when an idle CPU finds a runnable VCPU queued elsewhere
on the system.

Also during that time, 530 multi-core load balancing migrations 
happened.
That's about one such migration every 1.86 seconds. I'm somewhat 
surprised
that this costs 5% in performance of your benchmark. That said, the 
point
of this code is to balance a partially idle system and not to shuffle 
things
around too much so I'm happy to smooth the algorithm further to reduce 
the
number of these migrations.

I'll send another patch shortly.

On Dec 20, 2006, at 4:26, Xu, Anthony wrote:
> Before running KB
>
> (XEN)   migrate_queued                 = 169
> (XEN)   migrate_running                = 213
>
> (XEN) CPU[00]  tick=117181, sort=12233, sibling=0x1, core=0x5
>
>
> After running KB
>
> (XEN)   migrate_queued                 = 533
> (XEN)   migrate_running                = 743
>
> (XEN) CPU[00]  tick=215790, sort=42999, sibling=0x1, core=0x5
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