Date: Thu, 10 Jan 2008 11:07:12 +0100
From: Andi Kleen <ak@suse.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       Venki Pallipadi <venkatesh.pallipadi@intel.com>,
       suresh.b.siddha@intel.com, Arjan van de Ven <arjan@infradead.org>,
       Dave Jones <davej@redhat.com>
Subject: Re: CPA patchset
Message-ID: <20080110100712.GO25945@bingen.suse.de>
References: <20080103424.989432000@suse.de> <20080110093126.GA360@elte.hu> <20080110095337.GK25945@bingen.suse.de> <20080110100443.GB28209@elte.hu>
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On Thu, Jan 10, 2008 at 11:04:43AM +0100, Ingo Molnar wrote:
> 
> * Andi Kleen <ak@suse.de> wrote:
> 
> > >   WBINVD isnt particular fast (takes a few msecs), but why is that a 
> > >   problem? Drivers dont do high-frequency ioremap-ing. It's 
> > >   typically only done at driver/device startup and that's it.
> > 
> > Actually graphics drivers can do higher frequency allocation of WC 
> > memory (with PAT) support.
> 
> but that's not too smart: why dont they use WB plus cflush instead? 

Because they need to access it WC for performance.

> ioremap() will always be slow and we dont care about stupid uses of it.

Uninterruptible msec latencies are too slow even for slow path
initialization code imho.

-Andi
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