On 7/20/2015 8:00 PM, Jason Gunthorpe wrote:
On Mon, Jul 20, 2015 at 07:27:52PM +0300, Sagi Grimberg wrote:
I'm thinking now that this should have an input argument
of block_size. Maybe in the future ULPs would want to register
huge pages, it will be a shame to map it into PAGE_SIZE chunks...
Why wouldn't it just transparently support huge pages? sg seems to
have enough information.
I'm not sure I know how to do that, can you explain how please?
Scan the scatter list, if the pages are all the same length and
aligned on their length then that is the huge page size, otherwise use
4k.
Bleh... seems like a great effort just to find that out. Isn't it
better to just ask for a page_size arg?
Convert to a shift.
See if the driver supports that as a huge page size (currently
missing from our driver API).
It not missing, we have device attribute page_size_cap which is
a bitmask of supported page shifts (if I'm not mistaken).
Fill in the wr as you'd expect using the computed value as
wr.fast_reg.page_shift
Really, today nothing can use huge pages with IB_WR_FAST_REG_MR
because there is no way to negotiate with the driver the supported
page shift values. Hopefully your new version can get closer to
fixing that by taking the wr construction away from the caller.
It is negotiable. Most drivers don't negotiate it though... srp is
the only one who does it.
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