[PATCH] nvme-rdma: set ack timeout of RoCE to 262ms

[Christoph Hellwig]

On Fri, Aug 19, 2022 at 03:58:25PM +0800, Chao Leng wrote:
> Now the ack timeout of RoCE is 2 second(2^(18+1)*4us=2 second). In the
> case of low concurrency, if some packets lost due to network abnormal
> such as network rerouting, Optical fiber signal interference, etc,
> it will wait 2 second to try retransmitting the lost packets.
> As a result, the I/O latency is greater than 2 seconds.
> The I/O latency is so long for real-time transaction service. Indeed we
> do not have to wait so long time to make sure that packets are lost.
> Setting the ack timeout to 262ms(2^(15+1)*4us=262ms) is sufficient.

I'll leave people more familar with RoCE to judge the merits of this
change, but I really want a comment explaining the choice in the
source code.