On 4/13/21 5:01 PM, Alex Kogan wrote:

Hi, Andi.

Thanks for your comments!

quoted

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.

quoted

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.

quoted

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?

The CNA code, if enabled, will be in vmlinux, not in a kernel module. As 
a result, I think a module parameter will be no different from a kernel 
command line parameter in this regard.

Cheers,
Longman



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