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

On 1/24/20 11:58 PM, Paul E. McKenney wrote:

On Fri, Jan 24, 2020 at 09:17:05PM -0500, Waiman Long wrote:

quoted

On 1/24/20 8:59 PM, Waiman Long wrote:

quoted

quoted

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


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