Re: [for-next PATCH] infiniband:cma: add a parameter for the packet lifetime

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Nov 22, 2022 at 05:02:06PM +0800, Chao Leng wrote:
> Now the default packet lifetime(CMA_IBOE_PACKET_LIFETIME) is 18.
> That means the minimum ack timeout is 2 seconds(2^(18+1)*4us=2.097seconds).
> The packet lifetime means the maximum transmission time of packets
> on the network, the maximum transmission time of packets is closely
> related to the network. 2 seconds is too long for simple lossless networks.
> The packet lifetime should allow the user to adjust according to the
> network situation.
> So add a parameter for the packet lifetime.
> 
> Signed-off-by: Chao Leng <lengchao@huawei.com>
> ---
>  drivers/infiniband/core/cma.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> index cc2222b85c88..8e2ff5d610e3 100644
> --- a/drivers/infiniband/core/cma.c
> +++ b/drivers/infiniband/core/cma.c
> @@ -50,6 +50,10 @@ MODULE_LICENSE("Dual BSD/GPL");
>  #define CMA_IBOE_PACKET_LIFETIME 18
>  #define CMA_PREFERRED_ROCE_GID_TYPE IB_GID_TYPE_ROCE_UDP_ENCAP
>  
> +static unsigned char cma_packet_lifetime = CMA_IBOE_PACKET_LIFETIME;
> +module_param_named(packet_lifetime, cma_packet_lifetime, byte, 0644);
> +MODULE_PARM_DESC(packet_lifetime, "max transmission time of the packet");

No new module parameters

Maybe something in netlink would be appropriate, I'm not sure how
best to deal with this.

Really, the entire retransmit strategy in CM is not suitable for
ethernet networks, this is just one symptom.

Jason