Re: [PATCH net-next v6 1/7] net/smc: remove locks smc_client_lgr_pending and smc_server_lgr_pending

From: Wenjia Zhang <wenjia@linux.ibm.com>
To: "D. Wythe" <alibuda@linux.alibaba.com>,
	jaka@linux.ibm.com, kgraul@linux.ibm.com
Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org,
	linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org
Subject: Re: [PATCH net-next v6 1/7] net/smc: remove locks smc_client_lgr_pending and smc_server_lgr_pending
Date: Mon, 30 Jan 2023 22:10:46 +0100	[thread overview]
Message-ID: <bb50c952-6075-d838-0bc3-4848c12ad920@linux.ibm.com> (raw)
In-Reply-To: <a0de12ab-dd9a-acfe-4324-78815d6ebc35@linux.alibaba.com>


On 30.01.23 11:51, D. Wythe wrote:
> 
> 
> On 1/30/23 4:37 PM, Wenjia Zhang wrote:
>>
>>
>> On 29.01.23 16:11, D. Wythe wrote:
>>>
>>>
>>> On 11/26/22 5:03 PM, D.Wythe wrote:
>>>> From: "D. Wythe" <alibuda@linux.alibaba.com>
>>>>
>>>> This patch attempts to remove locks named smc_client_lgr_pending and
>>>> smc_server_lgr_pending, which aim to serialize the creation of link
>>>> group. However, once link group existed already, those locks are
>>>> meaningless, worse still, they make incoming connections have to be
>>>> queued one after the other.
>>>>
>>>> Now, the creation of link group is no longer generated by competition,
>>>> but allocated through following strategy.
>>>>
>>>
>>>
>>> Hi, all
>>>
>>> I have noticed that there may be some difficulties in the advancement 
>>> of this series of patches.
>>> I guess the main problem is to try remove the global lock in this 
>>> patch, the risks of removing locks
>>> do harm to SMC-D, at the same time, this patch of removing locks is 
>>> also a little too complex.
>>>
>>> So, I am considering that we can temporarily delay the advancement of 
>>> this patch. We can works on
>>> other patches first. Other patches are either simple enough or have 
>>> no obvious impact on SMC-D.
>>>
>>> What do you think?
>>>
>>> Best wishes.
>>> D. Wythe
>>>
>>>
>> Hi D. Wythe,
>>
>> that sounds good. Thank you for your consideration about SMC-D!
> 
> Hi Wenjia,
> 
> Thanks for your reply.
> 
>> Removing locks is indeed a big issue, those patches make us difficult 
>> to accept without thoroughly testing in every corner.
>>
>> Best
>> Wenjia
> 
> What do you mean by those patches? My plan is to delete the first patch 
> in this series,
> that is, 'remove locks smc_client_lgr_pending and 
> smc_server_lgr_pending', while other patches
> should be retained.
> 
> They has almost nothing impact on SMC-D or simple enough to be tested. 
> If you agree with this,
> I can then issue the next version as soon as possible to remove the 
> first patch, and I think
> we can quickly promote those patches.
> 
> Thanks.
> Wenjia
> 
Except for the removing locks of smc_client_lgr_pending and 
smc_server_lgr_pending, I'm still not that sure if running 
SMC_LLC_FLOW_RKEY concurrently could make the communication between our 
Linux and z/OS broken, that we can not test currently, though I really 
like this idea.
Sure, you can send the next version, I'll find a way to verify it.


> 
> 
>