Re: [PATCH 0/3][RFC] NUMA: add host side pinning

[Avi Kivity <avi@redhat.com>]

On 06/28/2010 07:20 PM, Anthony Liguori wrote:
>>
>>>>> To avoid this I'd like to see the pinning done from within QEMU. I 
>>>>> am not sure whether calling numactl via system() and friends is 
>>>>> OK, I'd prefer to run the syscalls directly (like in patch 3/3) 
>>>>> and pull the necessary options into the -numa pin,... command 
>>>>> line. We could mimic numactl's syntax here.
>>>>
>>>> Definitely not use system(), but IIRC numactl has a library interface?
>>> Right, that is what I include in patch 3/3 and use. I got the 
>>> impression Anthony wanted to avoid reimplementing parts of numactl, 
>>> especially enabling the full flexibility of the command line 
>>> interface (like specifying nodes, policies and interleaving).
>>> I want QEMU to use the library and pull the necessary options into 
>>> the -numa pin,... parsing, even if this means duplicating numactl 
>>> functionality.
>>>
>>
>> I agree with that.  It's a lot easier to use a single tool than to 
>> try to integrate things yourself, the unix tradition of grep | sort | 
>> uniq -c | sort -n notwithstanding.  Especially when one of the tools 
>> is qemu.
>
>
> I could disagree more here.  This is why we don't support CPU pinning 
> and instead provide PID information for each VCPU thread.

Good point.  That also allows setting priority, etc.

>
> The folks that want to use pinning are not notice users.  They are not 
> going to be happy unless you can make full use of existing tools.  
> That means replicating all of numactl's functionality (which is not 
> what the current patches do) or enable numactl to be used with a guest.
>

Yeah.  Unfortunately, that also forces us to use non-anonymous memory.  
So it isn't just where to put the functionality, it also has side effects.

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