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>
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index c7a78eef2..32c48a0 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -84,7 +84,8 @@
u32 p_proc; /* RPC procedure number */
kxdrproc_t p_encode; /* XDR encode function */
kxdrproc_t p_decode; /* XDR decode function */
- unsigned int p_bufsiz; /* req. buffer size */
+ unsigned int p_arglen; /* argument hdr length (u32) */
+ unsigned int p_replen; /* reply hdr length (u32) */
unsigned int p_count; /* call count */
unsigned int p_timer; /* Which RTT timer to use */
u32 p_statidx; /* Which procedure to account */