netdev - Re: [net-next 0/2] Deliver confirm/delete rkey message in parallel

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Date:   Tue, 21 Feb 2023 19:41:19 +0100
From:   Wenjia Zhang <wenjia@...ux.ibm.com>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com,
        jaka@...ux.ibm.com
Cc:     kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [net-next 0/2] Deliver confirm/delete rkey message in parallel



On 08.02.23 04:09, D. Wythe wrote:
> 
> 
> On 2/8/23 11:04 AM, D. Wythe wrote:
>>
>>
>> On 2/8/23 7:29 AM, Wenjia Zhang wrote:
>>>
>>>
>>> On 07.02.23 08:36, D. Wythe wrote:
>>>> From: "D. Wythe" <alibuda@...ux.alibaba.com>
>>>>
>>>> According to the SMC protocol specification, we know that all flows 
>>>> except
>>>> confirm_rkey adn delete_rkey are exclusive, confirm/delete rkey flows
>>>> can run concurrently (local and remote).
>>>>
>>>> However, although the protocol allows, all flows are actually mutually
>>>> exclusive in implementation, deus to we are waiting for LLC message
>>>> in serial.
>>>>
>>>> On the one hand, this implementation does not conform to the protocol
>>>> specification, on the other hand, this implementation aggravates the
>>>> time for establishing or destroying a SMC-R connection, connection
>>>> have to be queued in smc_llc_wait.
>>>>
>>>> This patch will improve the performance of the short link scenario
>>>> by about 5%. In fact, we all know that the performance bottleneck
>>>> of the short link scenario is not here.
>>>>
>>>> This patch try use rtokens or rkey to correlate a confirm/delete
>>>> rkey message with its response.
>>>>
>>>> This patch contains two parts.
>>>>
>>>> At first, we have added the process
>>>> of asynchronously waiting for the response of confirm/delete rkey
>>>> messages, using rtokens or rkey to be correlate with.
>>>>
>>>> And then, we try to send confirm/delete rkey message in parallel,
>>>> allowing parallel execution of start (remote) or initialization (local)
>>>> SMC_LLC_FLOW_RKEY flows.
>>>>
>>>> D. Wythe (2):
>>>>    net/smc: allow confirm/delete rkey response deliver multiplex
>>>>    net/smc: make SMC_LLC_FLOW_RKEY run concurrently
>>>>
>>>>   net/smc/smc_core.h |   1 +
>>>>   net/smc/smc_llc.c  | 263 
>>>> +++++++++++++++++++++++++++++++++++++++++------------
>>>>   net/smc/smc_llc.h  |   6 ++
>>>>   net/smc/smc_wr.c   |  10 --
>>>>   net/smc/smc_wr.h   |  10 ++
>>>>   5 files changed, 220 insertions(+), 70 deletions(-)
>>>>
>>>
>>> As we already discussed, on this changes we need to test them 
>>> carefully so that we have to be sure that the communicating with z/OS 
>>> should not be broken. We'll let you know as soon as the testing is 
>>> finished.
>>
>>
>> Hi, Wenjia
>>
>> Thanks again for your test.
>>
>> Considering that we have reached an agreement on protocol extension,
>> we can temporarily postpone this modification until we introduce the 
>> protocol extension
>> into the Linux community version. Then we can avoid the compatibility 
>> with z/OS.
>>
>>
>> Best wishes.
>> D. Wythe
>>
> 
> We can temporarily postpone this modification until we introduce the 
> protocol extension
> into the Linux community version IF we can't pass the z/OS compatible 
> test. :-)
> 
> Sorry for the problem in my description.
> 
> Thanks.
> D. Wythe
> 
Sorry that it took a bit lang to test. But it looks good to me. Please 
let me know if you still want to postpone it.

Best
Wenjia