Re: [PATCH v9 0/5] Add NUMA-awareness to qspinlock

Waiman Long
2020-01-25T19:42:00Z

On 1/24/20 11:58 PM, Paul E. McKenney wrote:
> On Fri, Jan 24, 2020 at 09:17:05PM -0500, Waiman Long wrote:
>> On 1/24/20 8:59 PM, Waiman Long wrote:
>>>> You called it! I will play with QEMU's -numa argument to see if I can get
>>>> CNA to run for me. Please accept my apologies for the false alarm.
>>>>
>>>> Thanx, Paul
>>>>
>>> CNA is not currently supported in a VM guest simply because the numa
>>> information is not reliable. You will have to run it on baremetal to
>>> test it. Sorry for that.
>> Correction. There is a command line option to force CNA lock to be used
>> in a VM. Use the "numa_spinlock=on" boot command line parameter.
> As I understand it, I need to use a series of -numa arguments to qemu
> combined with the numa_spinlock=on (or =1) on the kernel command line.
> If the kernel thinks that there is only one NUMA node, it appears to
> avoid doing CNA.
>
> Correct?
>
> Thanx, Paul
>
In auto-detection mode (the default), CNA will only be turned on when
paravirt qspinlock is not enabled first and there are at least 2 numa
nodes. The "numa_spinlock=on" option will force it on even when both of
the above conditions are false.

Cheers,
Longman