From: David Gibson <david@gibson.dropbear.id.au>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: Hugh Dickins <hugh@veritas.com>,
"Luck, Tony" <tony.luck@intel.com>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch] fix ia64 hugetlb_free_pgd_range
Date: Mon, 27 Feb 2006 11:27:42 +1100 [thread overview]
Message-ID: <20060227002742.GC24422@localhost.localdomain> (raw)
In-Reply-To: <B05667366EE6204181EABE9C1B1C0EB509C43438@scsmsx401.amr.corp.intel.com>
On Thu, Feb 23, 2006 at 10:30:39PM -0800, Chen, Kenneth W wrote:
> David Gibson wrote on Thursday, February 23, 2006 8:06 PM
> > But I don't see how not transforming them sometimes can be correct.
> > Suppose 'floor' is only a little way below 'addr' - addr will be
> > shifted down, but floor won't, so floor may now be above addr, which
> > will cause weird results.
> >
> > Afaict the *only* thing floor and ceiling are used for is bounds
> > checking the address range we're examining. How can that ever be
> > right if one address has been scaled down, but the other hasn't.
>
> The scale down isn't exactly on every address bits. Top 3 bits of
> virtual address are preserved.
Ah.. yes.
> #define htlbpage_to_page(x) (((unsigned long) REGION_NUMBER(x) << 61)
> | (REGION_OFFSET(x) >>
> (HPAGE_SHIFT-PAGE_SHIFT)))
>
> So scaled address for a hugetlb address will never be below unscaled
> normal page address. That is adjusted addr will never below unchanged
> floor.
Ok. So in fact it wouldn't matter whether or not addresses outside
the region are scaled, but conceptually they probably should be.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2006-02-27 0:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-24 6:30 [patch] fix ia64 hugetlb_free_pgd_range Chen, Kenneth W
2006-02-27 0:27 ` David Gibson [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-02-24 1:45 Chen, Kenneth W
2006-02-24 2:44 ` 'David Gibson'
2006-02-24 3:05 ` Chen, Kenneth W
2006-02-24 4:05 ` 'David Gibson'
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