linux-kernel - Re: [PATCH V4 0/7] x86/intel_rdt: Intel Cache Allocation Technology

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Date:	Thu, 26 Feb 2015 12:37:39 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Shivappa, Vikas" <vikas.shivappa@...el.com>,
	"Fleming, Matt" <matt.fleming@...el.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"tj@...nel.org" <tj@...nel.org>,
	"Auld, Will" <will.auld@...el.com>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	"Kleen, Andi" <andi.kleen@...el.com>,
	"Juvva, Kanaka D" <kanaka.d.juvva@...el.com>
Subject: Re: [PATCH V4 0/7] x86/intel_rdt: Intel Cache Allocation Technology


* Luck, Tony <tony.luck@...el.com> wrote:

> > The CAT thing was annoying already, but at least one 
> > can find that in the SDM, this RDT thing, not a single 
> > mention.
> 
> The problems of development at the bleeding edge. Would 
> you rather Linux sat on the sidelines until there are 
> enough Google hits from other users of new features?

Well, we'd prefer there to be A) published documentation, 
or, lacking published documentation, there be B) a coherent 
technical description within the code itself what the 
purpose is and how it all works conceptually (minus the 
buzzwords), so that we have a common starting point when 
reviewing it.

>    Technology: Intel Resource Director Technology
> 
>    Description: Allows the hypervisor to monitor Last Level Cache usage at the application
>    and VM levels.
> 
>    Benefit: Helps to improve performance and efficiency by providing better
>    information for scheduling, load balancing, and workload migration
> 
> Which isn't any help in evaluating this patch series :-(

No, but it already tells us more than the 0/7 description 
of the patch series did! It should be possible to improve 
on that.

Maintainers reverse engineering the implementation is an 
inefficient approach.

Thanks,

	Ingo
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