tree 2dd3f15bd9df537166a82777b0c95243b90b17e1
parent 511d2e8855a065c8251d0c140ebc353854f1929e
author Chuck Lever <chuck.lever@oracle.com> 1175201273 -0400
committer Trond Myklebust <Trond.Myklebust@netapp.com> 1177996630 -0700

SUNRPC: RPC buffer size estimates are too large

The RPC buffer size estimation logic in net/sunrpc/clnt.c always
significantly overestimates the requirements for the buffer size.
A little instrumentation demonstrated that in fact rpc_malloc was never
allocating the buffer from the mempool, but almost always called kmalloc.

To compute the size of the RPC buffer more precisely, split p_bufsiz into
two fields; one for the argument size, and one for the result size.

Then, compute the sum of the exact call and reply header sizes, and split
the RPC buffer precisely between the two.  That should keep almost all RPC
buffers within the 2KiB buffer mempool limit.

And, we can finally be rid of RPC_SLACK_SPACE!

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>