linux-kernel - Re: [Bug 10328] New: [regression] performance drop for glx

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Message-ID: <20080326052911.GA8173@elte.hu>
Date:	Wed, 26 Mar 2008 06:29:11 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, venkatesh.pallipadi@...el.com,
	arjan@...ux.intel.com, bug-track@...her-privat.net
Subject: Re: [Bug 10328] New: [regression] performance drop for glx


* Suresh Siddha <suresh.b.siddha@...el.com> wrote:

> fb drivers are using ioremap()/ioremap_nocache(), followed by mtrr_add 
> with WC attribute. Recent changes in page attribute code made both 
> ioremap()/ioremap_nocache() mappings as UC (instead of previous UC-). 
> This breaks the graphics performance, as the effective memory type is 
> UC instead of expected WC.
> 
> The correct way to fix this is to add ioremap_wc() (which uses UC- in 
> the absence of PAT kernel support and WC with PAT) and change all the 
> fb drivers to use this new ioremap_wc() API.
> 
> We can take this correct and longer route for post 2.6.25. For now, 
> revert back to the UC- behavior for ioremap/ioremap_nocache.

thanks Suresh, applied.

	Ingo
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