linux-kernel - Re: [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write

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Message-ID: <85c96e41-5a54-d3dd-bda4-d8ef9c28b1d8@intel.com>
Date:   Tue, 27 Feb 2018 13:01:18 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     fenghua.yu@...el.com, tony.luck@...el.com, gavin.hindman@...el.com,
        vikas.shivappa@...ux.intel.com, dave.hansen@...el.com,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write -
 pseudo-locking core

Hi Thomas,

On 2/20/2018 9:15 AM, Thomas Gleixner wrote:
> Let's look at the existing crtl/mon groups which are each represented by a
> directory already.
> 
>  - Adding a 'size' file to the ctrl groups would be a natural extension
>    which makes sense for regular cache allocations as well.
> 

I would like to clarify how you envision the value of "size" computed. A
resource group may have several resources associated with it. Some of
these resources may indeed overlap, for example, if there is L2 and L3
CAT capable resources on the system. Similarly when CDP is enabled,
there would be overlap in bitmasks referring to the same cache locations
but treated as different resources. Indeed, there may in the future be
some resources that are capable of allocation but not cache specifically
that could also be handled within a single resource group.

Summarizing all of these cases with a single "size" associated with the
resource group does not seem straightforward to me.

Reinette