Re: [PATCH] Documentation/kernel-parameters: Remove "Deprecated" from isolcpus=

[Waiman Long]

On 4/27/26 11:07 AM, Sebastian Andrzej Siewior wrote:
> The isolcpus= option has been marked as deprecated in 2017. Back then it
> was desired for the domain sub option to be configured dynamically at
> runtime instead using this boot command line which provides a static
> configuration. In the meantime this option was extended by other sub
> options which don't have runtime counterpart or it does not make sense
> to provide one.
>
> The deprecated part always referred to the default `domain' sub option
> but it was not obvious. Also the reasoning behind the deprecation is
> sort of dubious: There is nothing wrong with a static configuration if
> there is no desired to reconfigure. This is useful on systems which
> have one purpose and the CPU partition configuration is not changed for
> the entire lifetime.
>
> Remove the "Deprecated" note. Remove the part of the description which
> suggest to use cpuset.sched_load_balance and instead point to the
> documentation file which explains how to use cpusets to configure this
> at runtime.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
>   Documentation/admin-guide/kernel-parameters.txt | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 4d0f545fb3ec5..367931fe8da56 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2755,7 +2755,6 @@ Kernel parameters
>   			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
>   
>   	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
> -			[Deprecated - use cpusets instead]
>   			Format: [flag-list,]<cpu-list>
>   
>   			Specify one or more CPUs to isolate from disturbances
> @@ -2780,11 +2779,10 @@ Kernel parameters
>   			  Isolate from the general SMP balancing and scheduling
>   			  algorithms. Note that performing domain isolation this way
>   			  is irreversible: it's not possible to bring back a CPU to
> -			  the domains once isolated through isolcpus. It's strongly
> -			  advised to use cpusets instead to disable scheduler load
> -			  balancing through the "cpuset.sched_load_balance" file.
> -			  It offers a much more flexible interface where CPUs can
> -			  move in and out of an isolated set anytime.
> +			  the domains once isolated through this boot time
> +			  configuration. Use cpusets for a dynamic configuration
> +			  which can be altered at runtime. For details see
> +			  Documentation/admin-guide/cpu-isolation.rst.
>   
>   			  You can move a process onto or off an "isolated" CPU via
>   			  the CPU affinity syscalls or cpuset.
Acked-by: Waiman Long <longman@xxxxxxxxxx>