linux-kernel - Re: [PATCH][v3] x86/resctrl: Add task resctrl information display

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Message-ID: <alpine.DEB.2.21.1911201055260.6731@nanos.tec.linutronix.de>
Date:   Wed, 20 Nov 2019 12:22:46 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Chen Yu <yu.c.chen@...el.com>
cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chen Yu <yu.chen.surf@...il.com>
Subject: Re: [PATCH][v3] x86/resctrl: Add task resctrl information display

On Wed, 20 Nov 2019, Chen Yu wrote:
> Monitoring tools that want to find out which resctrl CTRL
> and MONITOR groups a task belongs to must currently read
> the "tasks" file in every group until they locate the process
> ID.
> 
> Add an additional file /proc/{pid}/resctrl to provide this
> information.
> 
> For example:
>  cat /proc/1193/resctrl
> CTRL_MON:/ctrl_grp0
> MON:/ctrl_grp0/mon_groups/mon_grp0

The formatting is quite ugly and I don't see why this needs to be multiple
lines and have these uppercase prefixes.

A task can only be part of one control group and of one monitoring group
which is associated to the control group. So just providing:

 1)   ""
 2)   "/"
 3)   "/mon_groups/mon0"
 4)   "/group0"
 5)   "/group0/mon_groups/mon1"

is simple and clear enough, i.e.:

#1: Resctrl is not available

#2: Task is part of the root group, task not associated to any monitoring
    group

#3: Task is part of the root group and monitoring group mon0

#4: Task is part of control group group0, task not associated to any
    monitoring group

#5: Task is part of control group group0 and monitoring group mon1

Hmm?

Thanks,

	tglx