linux-kernel - Re: [PATCH] x86_32: trim memory by updating e820 v3

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Message-Id: <200804280955.53592.jesse.barnes@intel.com>
Date:	Mon, 28 Apr 2008 09:55:53 -0700
From:	Jesse Barnes <jesse.barnes@...el.com>
To:	Mika Fischer <mika.fischer@...pnet.de>
Cc:	Ingo Molnar <mingo@...e.hu>, Gabriel C <nix.or.die@...glemail.com>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>, balajirrao@...il.com,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86_32: trim memory by updating e820 v3

On Monday, April 28, 2008 9:31 am Mika Fischer wrote:
> Jesse Barnes schrieb:
> > On Monday, April 28, 2008 6:53 am Ingo Molnar wrote:
> >> i think we should still try to make this a non-default option because
> >> modern Xorg should not have any need to touch MTRRs. Perhaps a .config
> >> dependent on CONFIG_DANGEROUS ;-)
> >
> > Well, not quite... we're still waiting on some way of getting WC
> > semantics for sysfs PCI files.  Suresh tells me something like that is
> > queued up, but until that hits the mainline X will still need to bang the
> > MTRRs to get decent performance.
>
> Do you happen to know if this new sysfs-way will work correctly in the
> case where the MTRRs explicitly say that the video-memory is uncachable?

It should, since we'll be using PAT to set the cache control in the sysfs 
case.

Jesse
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