linux-kernel - Re: [PATCH RFC] ioctl based CAT interface

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Message-ID: <20151116153711.GV17308@twins.programming.kicks-ass.net>
Date:	Mon, 16 Nov 2015 16:37:11 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	Luiz Capitulino <lcapitulino@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vikas Shivappa <vikas.shivappa@...el.com>,
	Tejun Heo <tj@...nel.org>, Yu Fenghua <fenghua.yu@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] ioctl based CAT interface

On Mon, Nov 16, 2015 at 12:37:08PM -0200, Marcelo Tosatti wrote:
> - position in bitmask represents nothing other than identification of
>   reservation and size, so:
> 
> 		group-A = 0x3F, group-B = 0xFF
>   is the same as
> 		group-A = 0xFC, group-B = 0xFF

No, the position very much matters; maybe not in this example, but it
does the moment you get overlapping bitmaps.

Picking which bits overlap determines which other groups are affected.

This is why a bitmap is more expressive than a single percentage.
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