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

Paul E. McKenney
2020-01-26T15:35:45Z

On Sat, Jan 25, 2020 at 02:41:39PM -0500, Waiman Long wrote:
> 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.

Hmmm...

Here is my kernel command line taken from the console log:

console=ttyS0 locktorture.onoff_interval=0 numa_spinlock=on locktorture.stat_interval=15 locktorture.shutdown_secs=1800 locktorture.verbose=1

Yet the string "Enabling CNA spinlock" does not appear.

Ah, idiot here needs to enable CONFIG_NUMA_AWARE_SPINLOCKS in his build.
Trying again with "--kconfig "CONFIG_NUMA_AWARE_SPINLOCKS=y"...

Thanx, Paul