linux-kernel - Re: [RFD] CAT user space interface revisited

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Date:	Fri, 20 Nov 2015 08:53:34 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Marcelo Tosatti <mtosatti@...hat.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Vikas Shivappa <vikas.shivappa@...el.com>,
	Tejun Heo <tj@...nel.org>, Yu Fenghua <fenghua.yu@...el.com>
Subject: Re: [RFD] CAT user space interface revisited

On Thu, 19 Nov 2015, Marcelo Tosatti wrote:
> On Thu, Nov 19, 2015 at 10:09:03AM +0100, Thomas Gleixner wrote:
> > On Wed, 18 Nov 2015, Marcelo Tosatti wrote
> > > Actually, there is a point that is useful: you might want the important
> > > application to share the L3 portion with HW (that HW DMAs into), and
> > > have only the application and the HW use that region.
> > > 
> > > So its a good point that controlling the exact position of the reservation 
> > > is important.
> > 
> > I'm glad you figured that out yourself. :)
> > 
> > Thanks,
> > 
> > 	tglx
> 
> The HW is a reclaimer of the L3 region shared with HW.
> 
> You might want to remove any threads from reclaiming from 
> that region.

I might for some threads, but certainly not for those which need to
access DMA buffers. Throwing away 10% of L3 just because you don't
want to deal with it at the interface level is hillarious.

Thanks,

	tglx
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