RFC how to use kernel procs/threads efficiently

[Rick Macklem]

Hi,

I have now dropped the client side of Flexible File Layout for pNFS into head
and I believe it is basically working.
Currently when talking to mirrored DS servers, it does the Write and Commit
RPCs to the mirrors serially. This works, but is inefficient w.r.t. elapsed to to
completion.

To do them concurrently, I need separate kernel processes/threads to do them.
I can think of two ways to do this:
1 - The code that I have running in projects/pnfs-planb-server for the pNFS server
      side does a kproc_create() to create a kernel process that does the RPC and
      then krpc_exit()s.
      - This was easy to code and works. However, I am concerned that there is
        going to be excessive overheads from doing all the kproc_create()s and
        kproc_exit()s?
       Anyone know if these calls will result in large overheads?
2 - I haven't coded this, but the other way I can think of to do this is to
      create a pool of threads (kthread_create() is sufficient in this case, I
      think?) and then hand each RPC to an available thread so it can do the RPC.
      - Other than a little more complex coding, the main issue I see with this one
        is "How many threads and when to create more/less of them.".

Anyhow, any comments w.r.t. the merits of either of the above approaches
(or a suggestion of other ways to do this) would be appreciated, rick