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

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Hi Emmanuel,

Thanks for your quick response.
I'm not familiar with scheduler, I'll study it. :-)

I put comments below, maybe it's not right. :-)

Emmanuel Ackaouy write on 2006年12月22日 0:23:
> 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.

>From the point of user of credit scheduler, it may be not regular migrations.
Because there are 4 CPU, and there are only 3 VCPU,

It would be unlikely that 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'm interested about this.
I'll investigate this.

> 
> I'll send another patch shortly.
Thanks again.

> 
> 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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