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Re: mmap'ed memory cacheable or uncheable

To: Jun Sun <jsun@mvista.com>
Subject: Re: mmap'ed memory cacheable or uncheable
From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Date: Tue, 29 Jul 2003 18:09:43 +0200 (MET DST)
Cc: Teresa Tao <Teresat@tridentmicro.com>, linux-mips@linux-mips.org
In-reply-to: <20030728142401.K25784@mvista.com>
Organization: Technical University of Gdansk
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
On Mon, 28 Jul 2003, Jun Sun wrote:

> > How about if I specify the following flags in my mmap routine just like 
> > what the pgprot_noncached micro did.
> >     pgprot_val(vma->vm_page_prot) &= ~_CACHE_MASK;
> >     pgprot_val(vma->vm_page_prot) |= _CACHE_UNCACHED;
> > 
> > Will this have kernel make the mmap'd memory non-cacheable? Or is there a 
> > mmap non-cacheable patch?
> 
> I think this might work.  Did you try it?  The performance will be bad
> though as mmap() is used widely by userland.

 See mmap_mem() for how to select between cached and uncached mmap()ing
cleanly. 

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +


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