Re: [PATCH 00/21] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking v2

Nicolas Saenz Julienne
2022-05-18T15:33:13Z

On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> This mixes up the RCU dynticks counter and the context tracking state
> updates into a single atomic instruction. This may serve several
> purposes:
>
> 1) Improve CPU isolation with deferring some disturbances until sensitive
> userspace workload completes and goes to the kernel. This can take
> several forms, for example smp_call_function_housekeeping() or
> on_each_housekeeping_cpu() to enqueue and execute work on all
> housekeeping CPUs. Then an atomic operation on ct->state can defer
> the work on nohz_full CPUs until they run in kernel (or IPI them
> if they are in kernel mode), see this proposal by Peter:
> https://lore.kernel.org/all/20210929151723.162004989@infradead.org/#r
>
> 2) Unearth sysidle (https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=sysidle.2017.05.11a&id=fe5ac724d81a3c7803e60c2232718f212f3f38d4)
> This feature allowed to shutdown the tick on the last housekeeping
> CPU once the rest of the system is fully idle. We needed some proper
> fully ordered context tracking for that.
>
> Inspired by Peterz: https://lore.kernel.org/all/20210929151723.162004989@infradead.org
>
> Passed 100 hours of TREE01.
>
> ---

For the whole series:

Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>

Thanks!

--
Nicolás Sáenz