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Date:   Mon, 3 Jul 2023 21:47:05 -0400
From:   Chuck Lever <cel@kernel.org>
To:     NeilBrown <neilb@suse.de>
Cc:     linux-nfs@vger.kernel.org, Chuck Lever <chuck.lever@oracle.com>,
        lorenzo@kernel.org, jlayton@redhat.com, david@fromorbit.com
Subject: Re: [PATCH v2 4/9] SUNRPC: Count ingress RPC messages per svc_pool
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On Tue, Jul 04, 2023 at 10:45:20AM +1000, NeilBrown wrote:
> On Tue, 04 Jul 2023, Chuck Lever wrote:
> > From: Chuck Lever <chuck.lever@oracle.com>
> > 
> > To get a sense of the average number of transport enqueue operations
> > needed to process an incoming RPC message, re-use the "packets" pool
> > stat. Track the number of complete RPC messages processed by each
> > thread pool.
> 
> If I understand this correctly, then I would say it differently.
> 
> I think there are either zero or one transport enqueue operations for
> each incoming RPC message.  Is that correct?  So the average would be in
> (0,1].
> Wouldn't it be more natural to talk about the average number of incoming
> RPC messages processed per enqueue operation?  This would be typically
> be around 1 on a lightly loaded server and would climb up as things get
> busy. 
> 
> Was there a reason you wrote it the way around that you did?

Yes: more than one enqueue is done per incoming RPC. For example,
svc_data_ready() enqueues, and so does svc_xprt_receive().

If the RPC requires more than one call to ->recvfrom() to complete
the receive operation, each one of those calls does an enqueue.