Re: [PATCH RFC 05/12] RDMA/cxgb4: Use for_each_sg_dma_page iterator on umem SGL

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On Sat, Jan 26, 2019 at 11:09:45AM -0600, Steve Wise wrote:
> 
> 
> > From: linux-rdma-owner@xxxxxxxxxxxxxxx <linux-rdma-
> > owner@xxxxxxxxxxxxxxx> On Behalf Of Shiraz Saleem
> > Sent: Saturday, January 26, 2019 10:59 AM
> > To: dledford@xxxxxxxxxx; jgg@xxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx
> > Cc: Shiraz, Saleem <shiraz.saleem@xxxxxxxxx>; Steve Wise
> > <swise@xxxxxxxxxxx>
> > Subject: [PATCH RFC 05/12] RDMA/cxgb4: Use for_each_sg_dma_page
> > iterator on umem SGL
> > 
> > From: "Shiraz, Saleem" <shiraz.saleem@xxxxxxxxx>
> > 
> > Use the for_each_sg_dma_page iterator variant to walk the umem
> > DMA-mapped SGL and get the page DMA address. This avoids the extra
> > loop to iterate pages in the SGE when for_each_sg iterator is used.
> > 
> > Additionally, purge umem->page_shift usage in the driver
> > as its only relevant for ODP MRs. Use system page size and
> > shift instead.
> 
> Hey Shiraz, Doesn't umem->page_shift allow registering huge pages
> efficiently?  IE is umem->page_shift set for the 2MB shift if the memory in
> this umem region is from the 2MB huge page pool? 

I think long ago this might have been some feavered dream, but it was
never implemented and never made any sense. How would the core code
know it driver supported the CPU's huge page size?

Shiraz's version to ineject huge pages into the driver is much better

Jason



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