From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Roland Dreier <rdreier@cisco.com>
Cc: Eli Cohen <eli@mellanox.co.il>,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
Subject: Re: FW: [PATCH] powerpc/mm: Export HPAGE_SHIFT
Date: Wed, 04 Feb 2009 12:50:48 +1100 [thread overview]
Message-ID: <1233712248.16867.131.camel@pasglop> (raw)
In-Reply-To: <ada8wonnh3t.fsf@cisco.com>
On Tue, 2009-02-03 at 17:08 -0800, Roland Dreier wrote:
> Forwarding Eli's patch below, since PowerPC guys may have missed it. I
> guess the question for Ben et al is whether there is any issue with
> exporting HPAGE_SHIFT for modules (can be EXPORT_SYMBOL_GPL if you feel
> it's an internal detail). It would probably make sense to roll this
> change into the mlx4 change that Eli alludes to below and merge through
> my tree (with ppc maintainer acks of course), rather than splitting this
> patch out and introducing cross-tree dependencies (and also separating
> the rationale for the change from the change itself).
>
> Thanks,
> Roland
>
>
> Drivers may want to take advantage of the large pages used for memory obtained
> from hugetlbfs. One example is mlx4_ib which can use much less MTT entries (in
> the order of HPAGE_SIZE / PAGE_SIZE) when registering such memory, thus scale
> significantly better when registering larger memory regions. Other drivers
> could also benefit from this.
Except that we support multiple large page sizes nowadays ... I think
the size can be specified per mountpoint of hugetlbfs no ? Thus things
like mellanox would have to query the page size used for a given
mapping.
Do the generic hugetlbfs code provides such an API ? If not, we may need
to add one.
Cheers,
Ben.
> Signed-off-by: Eli Cohen <eli@mellanox.co.il>
> ---
> arch/powerpc/mm/hash_utils_64.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 8d5b475..6cff8c7 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -104,6 +104,7 @@ int mmu_highuser_ssize = MMU_SEGSIZE_256M;
> u16 mmu_slb_size = 64;
> #ifdef CONFIG_HUGETLB_PAGE
> unsigned int HPAGE_SHIFT;
> +EXPORT_SYMBOL(HPAGE_SHIFT);
> #endif
> #ifdef CONFIG_PPC_64K_PAGES
> int mmu_ci_restrictions;
next prev parent reply other threads:[~2009-02-04 1:51 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090203164930.GA10101@mtls03>
2009-02-04 1:08 ` FW: [PATCH] powerpc/mm: Export HPAGE_SHIFT Roland Dreier
2009-02-04 1:50 ` Benjamin Herrenschmidt [this message]
2009-02-04 5:13 ` Andrew Morton
2009-02-04 5:31 ` Nick Piggin
2009-02-04 6:17 ` wli
2009-02-04 6:16 ` Roland Dreier
2009-02-04 6:26 ` Andrew Morton
2009-02-04 19:11 ` Roland Dreier
2009-02-04 21:00 ` wli
2009-02-04 21:31 ` Roland Dreier
2009-02-04 21:23 ` Andrew Morton
2009-02-04 23:55 ` Benjamin Herrenschmidt
2009-02-05 5:10 ` Roland Dreier
2009-02-05 5:24 ` Benjamin Herrenschmidt
2009-02-05 5:33 ` Roland Dreier
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