On 11/12/2013 9:33 AM, Or Gerlitz wrote:
On 12/11/2013 09:21, Nicholas A. Bellinger wrote:
The point is that if FMR is only required for future T10 PI support, why
not just disable it by default, instead of just avoiding it for the
small block count == 1 case..?
b/c for larger IOs (e.g that involves > 1 pages) it gives better
performance, since you don't need to use SGEs in for RDMA or
multiple RDMAs, just one RDMA and one SGE
Or.
Or is correct,
In the general case of large scatterlists it is better to perform fast
registration and use a single RDMA, but for small IOs (single entry)
skipping fast registration and using dma MR is faster as still you use a
single RDMA.
You are correct that in the future, this optimization will consider DIF
support as even for single entry scatterlists you need to register for
specific protection attributes.
Hope this helps,
Sagi.
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