== What Linux's RPC queue dump means, sort of

Since I went digging through the kernel source code [[yesterday
NFSClientDebuggingBits]], here is the meaning of the fields
in the RPC queue dump that you get any time you write to
((/proc/sys/sunrpc/rpc_debug)).

As far as I've been able to work out, the useful fields are:

|_. _-pid-_	| An internal RPC sequence number; it has nothing to
		  do with process PIDs, despite the name.
| _proc_	| The RPC procedure number being invoked, in decimal;
		  you can find which NFS action is which number from
		  places like ((include/linux/nfs3.h)) in the Linux
		  kernel source.
| _flgs_	| The RPC flags in hex; see ((include/linux/sunrpc/sched.h))
		  for the values.
| _status_	| Either 0 or a (negated) _errno_ if the task has hit an
		  error.
| _-client-_	| An opaque identifier for the client (literally, the
		  pointer to the RPC client structure in the kernel).
| _-prog-_	| What RPC facility is being invoked, in decimal; NFS
		  is RPC 'program' 100003. You can find out the program
		  numbers most easily with _rpcinfo -p_.
| _-timeout_	| The timeout, in jiffies.
| _-rpcwait_	| What the task is waiting for, if anything.

(The _--rqstp-_, _-action-_, and _--exit--_ fields are better off
ignored if you are not debugging the kernel; they are pointers to
internal kernel structures. About all you can do with them is see which
tasks have the same one.)

Unfortunately, there is no way to map from a particular RPC request to
the processes that are waiting on it; the _-pid-_ field is mostly useful
for matching things up with any other debugging messages that you have
the RPC system produce.