Date: Wed, 26 Mar 2008 06:29:11 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, bugme-daemon@bugzilla.kernel.org,
       linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
       venkatesh.pallipadi@intel.com, arjan@linux.intel.com,
       bug-track@fisher-privat.net
Subject: Re: [Bug 10328] New: [regression] performance drop for glx
Message-ID: <20080326052911.GA8173@elte.hu>
References: <bug-10328-27@http.bugzilla.kernel.org/> <20080325152809.e2b07251.akpm@linux-foundation.org> <20080326003912.GB3313@linux-os.sc.intel.com>
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* Suresh Siddha <suresh.b.siddha@intel.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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