Re: [PATCH 0/8] RFC: vcpu pinning at qemu start

[Anthony Liguori <anthony@codemonkey.ws>]

Glauber Costa wrote:
> Anthony Liguori wrote:
>
> No, it can't. Because at the time qemu starts, no vcpu -> thread id 
> relationship exists at all. And we don't know when it will.

Sure we do.  The vcpu -> thread id relationship is valid after 
kvm_init_ap() is called which is after machine init but before the 
select loop is entered for the first time.  Therefore, if you start qemu 
with -S, then connect on the monitor, and do an info cpus, you could be 
guaranteed to be told the mapping.

The threads are *idle* at this point so there's no harm if they were 
started on the "wrong" CPU.  You can now taskset to your hearts content 
and then when you're happy with placement, you can issue a 'cont' so 
that the VM actually starts running.  I saw "wrong" because you can 
still taskset the initial creation guaranteeing that the threads are 
created on the right group of physical CPUs, you just can't specify the 
exact mapping until you start interacting with the monitor.

Regards,

Anthony Liguori

>> Regards,
>>
>> Anthony Liguori
>>
>>>
>>>
>>
>


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