Re: [External] : Re: [PATCH v14 4/6] locking/qspinlock: Introduce starvation avoidance into CNA

[Andi Kleen]

> > 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.

Actually cpu_clock / sched_clock (see my other email). These should
be fast without corner cases and also monotonic.

> 
> > 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?

module_params can be changed at the command line too, so yes.

-Andi