From: Chuck Lever <chuck.lever@oracle.com>
To: Trond Myklebust <trondmy@hammerspace.com>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 1/2] SUNRPC: Fix up backchannel slot table accounting
Date: Wed, 17 Jul 2019 14:12:56 -0400 [thread overview]
Message-ID: <F138F86C-84FB-4FEA-8240-FDAD6FD4CE38@oracle.com> (raw)
In-Reply-To: <97e9839faef3d1bc901d4ced3d0cf2e0bf2a0bd1.camel@hammerspace.com>
> On Jul 17, 2019, at 1:19 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
>
> On Wed, 2019-07-17 at 09:55 -0400, Chuck Lever wrote:
>> Hi Trond-
>>
>>> On Jul 16, 2019, at 4:01 PM, Trond Myklebust <trondmy@gmail.com>
>>> wrote:
>>>
>>> Add a per-transport maximum limit in the socket case, and add
>>> helpers to allow the NFSv4 code to discover that limit.
>>
>> For RDMA, the number of credits is permitted to change during the
>> life
>> of the connection, so this is not a fixed limit for such transports.
>
> This is defining a maximum value, which is used for backchannel session
> slot negotiation.
>
>>
>> And, AFAICT, it's not necessary to know the transport's limit. The
>> lesser of the NFS backchannel and RPC/RDMA reverse credit limit will
>> be used.
>
> The server needs to know how many requests it can send in parallel on
> the back channel. If it sends too many, which it can and will do on
> TCP, then we currently break the connection, and so callbacks end up
> being dropped or missed altogether.
IIUC, RPC/RDMA has a fixed maximum constant. Would you like a patch at
some point that advertises that constant via ->bc_num_slots ?
--
Chuck Lever
next prev parent reply other threads:[~2019-07-17 18:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-16 20:01 [PATCH 1/2] SUNRPC: Fix up backchannel slot table accounting Trond Myklebust
2019-07-16 20:01 ` [PATCH 2/2] NFSv4: Don't use the zero stateid with layoutget Trond Myklebust
2019-07-17 13:55 ` [PATCH 1/2] SUNRPC: Fix up backchannel slot table accounting Chuck Lever
2019-07-17 17:19 ` Trond Myklebust
2019-07-17 18:12 ` Chuck Lever [this message]
2019-07-17 18:20 ` Trond Myklebust
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