Hi, Andi.

Thanks for your comments!

On Apr 13, 2021, at 2:03 AM, Andi Kleen [off-list ref] wrote:

Alex Kogan [off-list ref] writes:

quoted

+	numa_spinlock_threshold=	[NUMA, PV_OPS]
+			Set the time threshold in milliseconds for the
+			number of intra-node lock hand-offs before the
+			NUMA-aware spinlock is forced to be passed to
+			a thread on another NUMA node.	Valid values
+			are in the [1..100] range. Smaller values result
+			in a more fair, but less performant spinlock,
+			and vice versa. The default value is 10.

ms granularity seems very coarse grained for this. Surely
at some point of spinning you can afford a ktime_get? But ok.

We are reading time when we are at the head of the (main) queue, but
don’t have the lock yet. Not sure about the latency of ktime_get(), but
anything reasonably fast but not necessarily precise should work.

Could you turn that into a moduleparm which can be changed at runtime?
Would be strange to have to reboot just to play with this parameter

Yes, good suggestion, thanks.

This would also make the code a lot shorter I guess.

So you don’t think we need the command-line parameter, just the module_param?

Regards,
— Alex


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