Re: [PATCH 2/3] SUNRPC: Fix the TCP write space reservations for deferred requests

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Fri, 2009-06-19 at 18:23 -0400, J. Bruce Fields wrote:
> On Mon, May 18, 2009 at 05:47:56PM -0400, Trond Myklebust wrote:
> > Ensure that deferred requests are accounted for correctly by the write
> > space reservation mechanism. In order to avoid double counting, remove the
> > reservation when we defer the request, and save any calculated value, so
> > that we can restore it when the request is requeued.
> 
> I like that it does the addition to xpt_reserved in just one place
> instead of two, and carrying over the reserved_space is nice, but I
> don't understand the "double accounting" comment--where exactly is
> something counted twice?

Correct me if I'm wrong, but as far as I can see, the current code bumps
xpt_reserved every time you call svc_xprt_enqueue() irrespective of
whether or not you are going to process a new RPC call, or whether you
are processing a deferred call.

In the latter case, there doesn't appear to be any code that subtracts
from xpt_reserved prior to the re-enqueue process, hence my belief that
we are double counting those events...

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com