Hello  Kuniyuki.

On Mon, Jul 21, 2025 at 08:35:30PM +0000, Kuniyuki Iwashima <kuniyu@google.com> wrote:
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -1878,6 +1878,22 @@ The following nested keys are defined.
>  	Shows pressure stall information for memory. See
>  	:ref:`Documentation/accounting/psi.rst <psi>` for details.
>  
> +  memory.socket_isolated
> +	A read-write single value file which exists on non-root cgroups.
> +	The default value is "0".

Such attributes don't fit well into hierarchy.
What are expectations in non-root non-leaf cgroups?

Also the global limit is not so much different from a memcg limit
configured on ancestors. This provision thus looks like handling only
one particular case.

> +
> +	Some networking protocols (e.g., TCP, UDP) implement their own memory
> +	accounting for socket buffers.
> +
> +	This memory is also charged to a non-root cgroup as sock in memory.stat.
> +
> +	Since per-protocol limits such as /proc/sys/net/ipv4/tcp_mem and
> +	/proc/sys/net/ipv4/udp_mem are global, memory allocation for socket
> +	buffers may fail even when the cgroup has available memory.
> +
> +	Sockets created with socket_isolated set to 1 are no longer subject
> +	to these global protocol limits.

What happens when it's changed during lifetime of cgroup?

Thanks,
Michal