linux-kernel - Re: [RFC PATCH V2 11/22] x86/intel_rdt: Associate pseudo-locked regions with its domain

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Message-ID: <alpine.DEB.2.21.1802200017130.1853@nanos.tec.linutronix.de>
Date:   Tue, 20 Feb 2018 00:19:49 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Reinette Chatre <reinette.chatre@...el.com>
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 11/22] x86/intel_rdt: Associate pseudo-locked
 regions with its domain

On Mon, 19 Feb 2018, Reinette Chatre wrote:

> Hi Thomas,
> 
> On 2/19/2018 1:19 PM, Thomas Gleixner wrote:
> > On Tue, 13 Feb 2018, Reinette Chatre wrote:
> > 
> >> After a pseudo-locked region is locked it needs to be associated with
> >> the RDT domain representing the pseudo-locked cache so that its life
> >> cycle can be managed correctly.
> >>
> >> Only a single pseudo-locked region can exist on any cache instance so we
> >> maintain a single pointer to a pseudo-locked region from each RDT
> >> domain.
> > 
> > Why is only a single pseudo locked region possible? 
> 
> The setup of a pseudo-locked region requires the usage of wbinvd. If a
> second pseudo-locked region is thus attempted it will evict the
> pseudo-locked data of the first.

Why does it neeed wbinvd? wbinvd is a big hammer. What's wrong with clflush?

Thanks,

	tglx