On Thu, Apr 04, 2019 at 03:25:26PM +0000, Saleem, Shiraz wrote: > >Subject: Re: [PATCH rdma-next v1 2/6] RDMA/umem: Add API to find best driver > >supported page size in an MR > > > >On 19-Feb-19 16:57, Shiraz Saleem wrote: > >> This helper iterates through the SG list to find the best page size to > >> use from a bitmap of HW supported page sizes. Drivers that support > >> multiple page sizes, but not mixed pages in an MR can use this API. > >> > >> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxx> > >> Reviewed-by: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx> > >> Signed-off-by: Shiraz Saleem <shiraz.saleem@xxxxxxxxx> > > > >I've tested this patch comparing our existing efa_cont_pages() implementation vs > >ib_umem_find_single_pg_size() running different test suites: > > Thanks for testing! > > > > >Supported page sizes are anything between 4k to 2G. > >I'm using page shift to compare results of both functions (ilog2 the return value of > >ib_umem_find_single_pg_size). > > > >When huge pages are disabled, in many cases efa_cont_pages() returns page shift > >of 13 where ib_umem_find_single_pg_size() returns 12. Didn't see a test where > >ib_umem_find_single_pg_size() returns anything other than 12 (PAGE_SIZE). > > I wonder if the checks in place to guarantee offset into large page > align for user-space virt buf and phy buf is downgrading the page > bit. And that EFA might not need it. EFA doesn't have actual MRs with virtual addreses, so it probably doesn't care. Jason
