[PATCH RFC] nvme-rdma: support devices with queue size < 32

[Christoph Hellwig]

On Thu, Mar 23, 2017 at 10:04:09AM +0100, Marta Rybczynska wrote:
> In the case of small NVMe-oF queue size (<32) we may enter
> a deadlock caused by the fact that the IB completions aren't sent
> waiting for 32 and the send queue will fill up.
> 
> The error is seen as (using mlx5):
> [ 2048.693355] mlx5_0:mlx5_ib_post_send:3765:(pid 7273):
> [ 2048.693360] nvme nvme1: nvme_rdma_post_send failed with error code -12
> 
> The patch doesn't change the behaviour for remote devices with
> larger queues.

Thanks, this looks useful.  But wouldn't it be better to do something
like queue_size divided by 2 or 4 to get a better refill latency?