netdev - Re: [MAINLINE 0/2] Enable DIM for legacy ULPs and use it in RDS

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Message-ID: <8d19d735-c2a8-456a-ac97-7f8d86cd7ed1@linux.dev>
Date: Thu, 26 Sep 2024 23:25:33 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Leon Romanovsky <leon@...nel.org>
Cc: Haakon Bugge <haakon.bugge@...cle.com>,
 Christoph Hellwig <hch@...radead.org>, Jason Gunthorpe <jgg@...pe.ca>,
 Allison Henderson <allison.henderson@...cle.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 OFED mailing list <linux-rdma@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "rds-devel@....oracle.com" <rds-devel@....oracle.com>
Subject: Re: [MAINLINE 0/2] Enable DIM for legacy ULPs and use it in RDS

在 2024/9/25 17:26, Leon Romanovsky 写道:
> On Wed, Sep 25, 2024 at 10:04:21AM +0800, Zhu Yanjun wrote:
>> 在 2024/9/24 23:16, Haakon Bugge 写道:
>>>
>>>
>>>> On 24 Sep 2024, at 15:59, Zhu Yanjun <yanjun.zhu@...ux.dev> wrote:
>>>>
>>>> 在 2024/9/24 14:54, Christoph Hellwig 写道:
>>>>> On Tue, Sep 24, 2024 at 09:58:24AM +0800, Zhu Yanjun wrote:
>>>>>> The users that I mentioned is not in the kernel tree.
>>>>> And why do you think that would matter the slightest?
>>>>
>>>> I noticed that the same cq functions are used. And I also made tests with this patch series. Without this patch series, dim mechanism will not be invoked.
>>>
>>> Christoph alluded to say: Do not modify the old cq_create_cq() code in order to support DIM, it is better to change the ULP to use ib_alloc_cq(), and get DIM enabled that way.
>>
>> Hi, Haakon
>>
>> To be honest, I like your original commit that enable DIM for legacy ULPs
>> because this can fix this problem once for all and improve the old
>> ib_create_cq function.
>>
>> The idea from Christoph will cause a lot of changes in ULPs. I am not very
>> sure if these changes cause risks or not.
>>
>> Thus, I prefer to your original commit. But I will follow the advice from
>> Leon and Jason.
> 
> Christoph was very clear and he summarized our position very well. We
> said similar thing to SMC folks in 2022 [1] and RDS is no different here.

Thanks, Leon. I will read this link carefully.

> 
> So no, "old ib_create_cq" shouldn't be used by ULPs.

Got it. I have replaced ib_create_cq with ib cq pool APIs. Perhaps 
drivers/infiniband/ulp/srpt/ib_srpt.c is a good example to use ib cq 
pool APIs.

Best Regards,
Zhu Yanjun

> 
> Thanks
> 
> [1] https://lore.kernel.org/netdev/YePesYRnrKCh1vFy@unreal/
> 
>>
>> Zhu Yanjun
>>
>>>
>>>
>>> Thxs, Håkon
>>>
>>
>>