From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Kumar Gala <galak@kernel.crashing.org>
Cc: linux-ppc list <linuxppc-dev@ozlabs.org>, David Gibson <dwg@au1.ibm.com>
Subject: Re: using different format for hugetlbfs
Date: Fri, 04 Dec 2009 19:58:56 +1100 [thread overview]
Message-ID: <1259917136.2076.1264.camel@pasglop> (raw)
In-Reply-To: <230774E3-2D94-44DA-85AC-151485996789@kernel.crashing.org>
On Fri, 2009-12-04 at 01:18 -0600, Kumar Gala wrote:
> Ben, David,
>
> If we want to support true 4G/4G split on ppc32 using the MSB of the
> address to determine of the pgd_t is for hugetlbfs isn't going to
> work. Since every pointer in the pgd_t -> pud_t -> pmd_t is point to
> at least a 4K page I would think the low order 12-bits should always
> be 0.
On 32 bit maybe. On 64, the pg/u/md's can be smaller. I don't really
want to have a different encoding for both types though.
> Could we use something like:
>
> addr[0:51] || shift [52:59] || flags [60:63]
>
> with the LSB flag being 'normal pointer' vs 'hugetlbfs mangled
> pointer'. Seems like shift will at most be 64 so 8-bits should cover
> it.
Cheers,
Ben.
next prev parent reply other threads:[~2009-12-04 8:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-04 7:18 using different format for hugetlbfs Kumar Gala
2009-12-04 8:58 ` Benjamin Herrenschmidt [this message]
2009-12-04 14:09 ` Kumar Gala
2009-12-04 21:25 ` Benjamin Herrenschmidt
2009-12-06 3:05 ` Kumar Gala
2009-12-07 1:04 ` Benjamin Herrenschmidt
2009-12-08 2:28 ` David Gibson
2009-12-08 15:44 ` Kumar Gala
2009-12-09 2:00 ` David Gibson
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