linux-kernel - RE: [PATCH] x86/resctrl: mba_MBps: Fall back to total b/w if local b/w unavailable

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Message-ID: <SJ1PR11MB6083F84A3A83F26F4111900EFCDFA@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Tue, 24 Oct 2023 18:24:50 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "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>
CC:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....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] x86/resctrl: mba_MBps: Fall back to total b/w if local
 b/w unavailable

> If local bandwidth measurement is not available, do not give up on
> providing the "mba_MBps" feedback option completely, make the code fall
> back to using total bandwidth.

N.B. I don't have a system yet that does this. Tested using boot command line
"clearcpuid=cqm_mbm_local" argument to the kernel to fake the non-prescence
of local bandwidth monitoring.

-Tony