Re: [PATCH 2/2][v2] x86/resctrl: Add task resctrl information display

[Borislav Petkov <bp@alien8.de>]

On Sat, Nov 16, 2019 at 11:01:12PM +0800, Ryan Chen wrote:
> Right, we can return 'blank' to user and let the user to parse the information.

There is nothing to parse - the task doesn't belong to any groups. That's it.

> And there is a similar behavior in cgroup that, for kernel thread that
> does not belong
> to any cgroup, /proc/{pid}/cgroup just show 'blank' without returning an error.

By 'blank' I assume you mean the empty string '' ?

> Yes, only when PROC_FS is set, /proc/{pid}/resctrl
> can be displayed. However, CPU_RESCTRL might not
> depend on proc fs, it is possible that the CPU_RESCTRL
> is enabled but without PROC_FS set. If I understand correctly,
>  CPU_RESCTRL is the 'root' config for X86_CPU_RESCTRL,
> after reading this thread:
> https://lists.gt.net/linux/kernel/3211659

I'm not sure I know what you mean here. There's no CPU_RESCTRL option - you've
added it in the previous patch:

[ ~/kernel/linux> git grep -E CONFIG_CPU_RESCTRL
[ ~/kernel/linux> git grep -E "\WCPU_RESCTRL"
[ ~/kernel/linux>

And if you want to use that option in proc/, then it needs
to depend on PROC_FS, like the the example I gave you with
CONFIG_PROC_PID_ARCH_STATUS.

Or do you mean something else?

>  If this is the case, shall we add the new file at kernel/resctrl/resctrl.c?
> And the generic proc_resctrl_show() could be put into this file. In the future
> the generic code for resctrl could be added/moved to kernel/resctrl/resctrl.c

Not worth it for a single function. Leave it in
arch/x86/kernel/cpu/resctrl/rdtgroup.c where you had it.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette