For a given hardware queue size, only allow a quarter of the queue size
to be returned as completions in a single call to
spdk_nvme_qpair_process_completions(), and adjust num_trackers to match
so that num_trackers + max_completions_cap doesn't exceed the hardware
completion queue size. This ensures that there is room in the
completion queue if new I/O is issued in response to completions before
we ring the completion queue doorbell.
The choice of 1/4 queue size is arbitrary; this seems to be a good
compromise between completion batch size and number of trackers.
Change-Id: I2c5aad7b98bfc8b33e53242240b2c9254fa05b4e
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-on: https://review.gerrithub.io/393529
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
5e86c80951