linux-kernel - RE: [PATCH v4 13/18] x86/intel_rdt: Add mkdir to resctrl file system

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F3A20010B@ORSMSX114.amr.corp.intel.com>
Date:   Mon, 17 Oct 2016 23:00:48 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Anvin, H Peter" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        "Borislav Petkov" <bp@...e.de>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Nilay Vaish <nilayvaish@...il.com>, Shaohua Li <shli@...com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: RE: [PATCH v4 13/18] x86/intel_rdt: Add mkdir to resctrl file system

> So how are we going to deal with that in the schematas? Assume the L3=16
> and L2=8 case(no CDP). So effectively any write of L2 to CLOSID=0 will
> affect the setting of L2 in CLOSID=8.
>
> Will the code tell the user that L2 cannot be set for CLOSID >= 8? 
>
> Will it print the setting of CLOSID - 8 for CLOSID >= 8 when you read the
> schemata file of CLOSID >= 8?

The default and first 7 directories you make will have lines in schemata for
both L3 and L2.  The next 8 will just have L3 (and won't let you add L2).

> And of course this becomes very interesting when CLOSID 1 is deleted, then
> what happens to CLOSID 9? Not to talk about the case when CLOSID 1 is
> reused again.

Deleting CLOSID 1 won't affect CLOSID 9.  When you make a new directory
that gets allocated CLOSID 1, it will have both L3 and L2 lines.

-Tony