Messages in this thread |  | | | Date | Tue, 3 Feb 2009 21:13:29 -0800 | | From | Andrew Morton <> | | Subject | Re: FW: [PATCH] powerpc/mm: Export HPAGE_SHIFT |
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On Wed, 04 Feb 2009 12:50:48 +1100 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> 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. >
I think it's something like
huge_page_size(page_hstate(page))
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