From: Michael Ellerman <michael@ellerman.id.au>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org, Paul Mackerras <paulus@samba.org>,
Liu Ping Fan <kernelfans@gmail.com>
Subject: Re: [PATCH 2/2] powerpc: mm: change pgtable index size for 64K page
Date: Fri, 22 Nov 2013 13:06:08 +1100 [thread overview]
Message-ID: <1385085968.26020.0.camel@concordia> (raw)
In-Reply-To: <1385077581.4882.30.camel@pasglop>
On Fri, 2013-11-22 at 10:46 +1100, Benjamin Herrenschmidt wrote:
> On Fri, 2013-11-22 at 09:11 +1100, Paul Mackerras wrote:
> > On Thu, Nov 21, 2013 at 10:17:55AM +0800, Liu Ping Fan wrote:
> > > For 64K page, we waste half of the pte_t page. With this patch, after
> > > changing PGD_INDEX_SIZE from 12 to 11, PTE_INDEX_SIZE from 8 to 9,
> > > we can improve the usage of pte_t page and shrink the continuous phys
> > > size for pgd_t.
>
> Also you did you miss that we use the second half to store the
> per-subpage hash info when using 64k on top of HW 4k ?
Given the subtleties perhaps a nice big block comment is in order ? :)
cheers
next prev parent reply other threads:[~2013-11-22 2:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-21 2:17 [PATCH 1/2] powerpc: mm: use macro PGTABLE_EADDR_SIZE instead of digital Liu Ping Fan
2013-11-21 2:17 ` [PATCH 2/2] powerpc: mm: change pgtable index size for 64K page Liu Ping Fan
2013-11-21 22:11 ` Paul Mackerras
2013-11-21 23:46 ` Benjamin Herrenschmidt
2013-11-22 2:06 ` Michael Ellerman [this message]
2014-04-30 5:30 ` [PATCH 1/2] powerpc: mm: use macro PGTABLE_EADDR_SIZE instead of digital Aneesh Kumar K.V
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