[rds-devel] what is rdma immediate data and how is it used ?

[Richard Frank]

Or Gerlitz wrote:
> Richard Frank wrote:
>> Our planned use of immediate data (notification message of rdma 
>> completion) keeps the immediate data (msg) separate from the rdma data.
>
> Isn't this somehow non optimal for the case of rdma-write (disk read)?

In the rdma write case (data to client) the immediate data identifies 
the request that is completing.

In the rdma read case (data from client), the rdma server  can 
optionally send notification (immediate data).  The rdma server could - 
for example - let the client know that the client buffer is no longer in 
use - the data is now on the rdma server - and if it is in non-volatile 
memory - it could indicate that the clients request is complete.  From 
the RDS driver perspective, the immediate data rm (even if zero client 
data) also provides a mechanism to auto free the key setup for the rdma 
xfer (resource management). If moving the data from the rdma server to 
persistent storage takes additional work - then when this work is 
complete - a separate message is sent to the client indicating 
completion of the request.




>
> Or.
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