Re: [PATCH v2 2/5] Introducing qpw_lock() and per-cpu queue & flush work

Vlastimil Babka (SUSE)
2026-03-11T07:58:14Z

On 3/2/26 16:49, Marcelo Tosatti wrote:
> Index: linux/Documentation/admin-guide/kernel-parameters.txt
> ===================================================================
> --- linux.orig/Documentation/admin-guide/kernel-parameters.txt
> +++ linux/Documentation/admin-guide/kernel-parameters.txt
> @@ -2840,6 +2840,16 @@ Kernel parameters
>
> The format of <cpu-list> is described above.
>
> + qpw= [KNL,SMP] Select a behavior on per-CPU resource sharing
> + and remote interference mechanism on a kernel built with
> + CONFIG_QPW.
> + Format: { "0" | "1" }
> + 0 - local_lock() + queue_work_on(remote_cpu)
> + 1 - spin_lock() for both local and remote operations
> +
> + Selecting 1 may be interesting for systems that want
> + to avoid interruption & context switches from IPIs.
Requiring a new boot option is always a nuissance. The cpu isolation is
AFAIK difficult enough to setup already. Could the default be that qpw will
auto-enable if there are isolated cpus configured? The option could still be
useful for overriding that automatic decision to both 0 and 1 for testing
etc, but not requried for the expected usecase?