The upcoming rescan implementation will
do scan I/O on existing I/O virtqueues.
To handle scan cleanly, we need to queue
scan I/O if virtqueues are full.
The heuristics for resending I/O should
be sufficient for all real case scenarios.
A scan I/O consists of either 2 or 3 iovs.
A raw I/O consists of at least 2
descriptors. Since most I/O requests
contain some additional payload, in 99%
of cases the scan I/O will be successfully
resent after polling a single I/O response.
To handle the remaining 1%, we try to
resend a scan I/O up to SCAN_REQUEST_RETRIES
(currently = 5) times.
Change-Id: I8c84ed1d109d9f403c9d7b8efabb904eb26183db
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/392174
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
8b0f049e85