Re: [PATCH v5 04/16] fs/resctrl: Introduce kernel mode policy enum

[Babu Moger]

Hi Reinette,

On 9/16/26 00:14, Reinette Chatre wrote:
> Hi Babu,
>
> On 8/26/26 12:32 PM, Babu Moger wrote:
> > Kernel mode traffic can use different allocation and monitoring
>
> "traffic" -> "work" to not imply this is just about memory traffic but
> also includes cache allocation?

Sure.

> > associations than the originating user task. On x86, Privilege Level Zero
> > Association (PLZA) enables the kernel to switch to a different CLOSID/RMID
> > when entering kernel mode.
> >
> > Architectures need a common way to name kernel modes before resctrl
> > can report what is active or what the platform supports.
> >
> > Introduce enum resctrl_kernel_mode:
> >    - RESCTRL_INHERIT_USER: Kernel mode inherits allocation and monitoring
> >      from the user task.
> >    - RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU: Kernel mode may use allocation
> >      and/or monitoring associations that differ from the user task. On x86,
> >      CLOSID and RMID can be configured independently for kernel mode.
> >
> > Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> > ---
>
> ...
>
> > ---
> >   include/linux/resctrl.h | 25 +++++++++++++++++++++++++
> >   1 file changed, 25 insertions(+)
> >
> > diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> > index dd09c2ce9a0f..4245d1e65ccc 100644
> > --- a/include/linux/resctrl.h
> > +++ b/include/linux/resctrl.h
> > @@ -704,6 +704,31 @@ int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable);
> >    */
> >   bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r);
> >   
> > +/**
> > + * enum resctrl_kernel_mode - Kernel mode control and monitoring association.
> > + *
> > + * @RESCTRL_INHERIT_USER:
> > + *     Kernel mode inherits both allocation and monitoring associations
> > + *     from the user space task. On x86, kernel uses the same CLOSID and
> > + *     RMID as the user-space task.
> > + *
> > + * @RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU:
> > + *     Kernel mode may use allocation and monitoring associations that
>
> Why is this "may use"? Could this be made more accurate? Consider, for
> example:
> 	All kernel mode work uses the same allocation and/or monitoring
> 	association via an assigned CTRL_MON or MON group. The mode can
> 	be enabled/disabled per-CPU. When the mode is disabled on a CPU
> 	then the kernel work on that CPU inherits the allocation and
> 	monitoring association from the user space task, effectively the
> 	kernel mode becomes RESCTRL_INHERIT_USER on that CPU.

Sure. Thanks.

> > + *     differ from the user task. On x86, CLOSID and RMID are configured
> > + *     independently; either or both may differ from user mode.
>
> Please first provide all details that support what resctrl fs exposes to
> user space before, if at all, adding any x86 specific details.
Sure.

> > + *
> > + *     All online CPUs are included by default. A subset may be selected
> > + *     through the resctrl group interface, and a CTRL_MON or MON group
> > + *     may be associated with this mode.
>
> Please note that the word "associated" appears in multiple contexts here.

"assigned" might work better here.

> > + */
> > +enum resctrl_kernel_mode {
> > +	RESCTRL_INHERIT_USER,
> > +	RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU,
>
> Something that stands out in this series is the multiple occurrences of
> "assigned" in the new interface. What do you think of just dropping
> "assign" from the kernel mode name?

Actually, I was thinking about shortening the name here.

Let's remove "assign" from here.

Thanks
Babu
.