linux-kernel - RE: [PATCH v5] x86/resctrl: Add event choices for mba

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Message-ID: <SJ1PR11MB60839F92B1C15A659CD32478FC86A@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Mon, 4 Dec 2023 19:45:40 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "babu.moger@....com" <babu.moger@....com>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        "Jonathan Corbet" <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v5] x86/resctrl: Add event choices for mba_MBps

> Yes. I saw the thread. Even then I feel having two similar options can
> cause confusion. I feel it is enough just to solve the original problem.
> Giving more options to a corner cases is a overkill in my opinion.

The "original" problem was systems without "local" bandwidth event. I
wanted to give a way for users of mba_MBps to still have some way to
use it (assuming that "total" bandwidth event was present).

Reinette suggested that some people might want to use "total", even
on systems that support "local". I firmly agree with that.  It is easy to
construct scenarios where most bandwidth is to a remote node. using
"local" event will do nothing to throttle in these case. I'm not at all sure
why "local" event was picked. There's nothing in the LKML threads to
give clues.

I proposed a mount option "total" as a modifier to be used in conjunction
with "mba_MBps". Reinette said it was too generic. Her suggestion was
to add "mba_MBps_total" to be used instead of "mba_MBps".

Is that where I should have gone, instead of "mba_MBps={local|total}"?

-Tony