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Date:   Thu, 21 Jan 2021 20:58:13 +0200
From:   Dan Aloni <dan@kernelim.com>
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Jim Foraker <foraker1@llnl.gov>,
        Ben Woodard <woodard@redhat.com>
Subject: Re: [RFC] NFSv3 RDMA multipath enhancements
Message-ID: <20210121185813.GA3135951@gmail.com>
References: <20210112141706.GA3146539@gmail.com>
 <3AB7389B-2EA9-4894-9656-9C8512166E0E@oracle.com>
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On Wed, Jan 13, 2021 at 09:59:58AM -0500, Chuck Lever wrote:
> > To my understanding NFSv4.x with pNFS has advanced dynamic transport
> > management logic along file layouts supporting stripe over file offsets,
> > however there are cases in which we would like to achieve good
> > performance even with the older protocol.
>
> Hi Dan, my curiosity is piqued about the RPC request dispatch changes
> you have in mind. Can you post them here for review?

These changes depend on the initial changes I'd like to contribute. The
gist of them concerns the xprt multipath algorithm where in addition to
round robin, we add further considerations regarding transport picking.
For example, for data IOs, the NUMA node to which the memory pages
attached to the RPC request may be used to pick a transport with an
outgoing local port that is closer to that memory in the server
architecture compared to the other local ports. So the idea is to lessen
data transfer bottlenecks in hardware.

> Also, if you can tell us, what NFS server supports NFS/RDMA but not
> NFSv4 ?

For example, there are VAST Data clusters currently supporting NFSv3 (as
one logical server), with the NFSv4 support coming soon.

--
Dan Aloni