[RFC PATCH 0/5] nvme: reduce repetitive calls in fast path

[Christoph Hellwig]

On Mon, Jul 06, 2020 at 04:15:19PM -0700, Chaitanya Kulkarni wrote:
> Hi Christoph/James/Keith/Sagi,
> 
> While reviewing other patch-series I found that there are repetitive
> calls to blk_rq_nr_phys_segments() in the fast path for NVMe Transports 
> (pci, rdma, fc, loop). We should try and avoid as many repetitive checks
> in the fast-path as possible.
> 
> This patch-series reduces multiple calls and minimizes the repetitive
> checks in blk_rq_nr_phys_segments() for NVMe transports.
> 
> P.S. Tagging it as an RFC since I've not tested rdma/tcp/fc part, if we
> agree to get this in I'll put more effort in testing.

blk_rq_nr_phys_segments is pretty trivial - just a branch and struct
field access.  Does this make any kind of difference?