[openib-general] RFC: SDP plans

[Michael S. Tsirkin]

I started preparing a stable linux SDP implementation,
with the eye towards mainline inclusion.

The idea is to get to a drastically simple code base and get this admitted in
mainline, then add enhancements.

The plan (as compared to existing SDP implementation) includes:
- Use CMA API
- Reuse generic code from sock.c
  SO_SNDBUF/SO_RCVBUF should work properly
- Use sock_lock_t and simple spin_lock_bh for socket locking
- Use skbuff and standard skbuff queues (in struct sock)
  for incoming/outgoing messages
- Implement transport-level queues by simple circular buffer,
  attach BSDH by s/g
- Set socket bits to signal the need for control messages
- Single CQ, perform all CQ polling from interrupt context
- Code must be sparse-clean, keep network data in __beXX structures
- Proper use of DMA API
- Use sysfs for statistics, entry per socket
- Only support the BCopy mode for starters -
  any advertisements will be answered with sendsm
- Only support synchronous operations for starters: applications
  can use userspace AIO emulation, and hopefully generic AIO support
  in kernel will mature meanwhile.

-- 
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies