Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <7d30b552-a737-9f19-dea8-26978a6601ea@linux.dev>
Date:   Mon, 12 Sep 2022 16:29:51 +0800
MIME-Version: 1.0
Subject: Re: [RFC PATCH 2/7] RDMA/rxe: Convert the triple tasklets to
 workqueues
To:     "matsuda-daisuke@fujitsu.com" <matsuda-daisuke@fujitsu.com>,
        'Bart Van Assche' <bvanassche@acm.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "leonro@nvidia.com" <leonro@nvidia.com>,
        "jgg@nvidia.com" <jgg@nvidia.com>,
        "zyjzyj2000@gmail.com" <zyjzyj2000@gmail.com>
Cc:     "nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "rpearsonhpe@gmail.com" <rpearsonhpe@gmail.com>,
        "yangx.jy@fujitsu.com" <yangx.jy@fujitsu.com>,
        "lizhijian@fujitsu.com" <lizhijian@fujitsu.com>,
        "y-goto@fujitsu.com" <y-goto@fujitsu.com>
References: <cover.1662461897.git.matsuda-daisuke@fujitsu.com>
 <41e5476f4f14a0b77f4a8c3826e3ef943bf7c173.1662461897.git.matsuda-daisuke@fujitsu.com>
 <0b3366e6-c0ae-7242-5006-b638e629972d@linux.dev>
 <fd1d7c49-a090-e8c7-415b-dfcda94ace9d@acm.org>
 <TYCPR01MB8455D739FC9FB034E3485C87E5449@TYCPR01MB8455.jpnprd01.prod.outlook.com>
From:   Yanjun Zhu <yanjun.zhu@linux.dev>
In-Reply-To: <TYCPR01MB8455D739FC9FB034E3485C87E5449@TYCPR01MB8455.jpnprd01.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk


在 2022/9/12 15:58, matsuda-daisuke@fujitsu.com 写道:
> On Mon, Sep 12, 2022 12:09 AM Bart Van Assche wrote:
>> On 9/11/22 00:10, Yanjun Zhu wrote:
>>> I also implemented a workqueue for rxe. IMO, can we add a variable to
>>> decide to use tasklet or workqueue?
>>>
>>> If user prefer using tasklet, he can set the variable to use
>>> tasklet. And the default is tasklet. Set the variable to another
>>> value to use workqueue.
> That's an interesting idea, but I am not sure how users specify it.
> IIRC, tasklets are generated when rdma link is added, typically by
> executing ' rdma link add' command. I don't think we can add
> an device specific option to the utility(iproute2/rdma).

In my workqueue implementation, I used a sysctl variable to set a value 
to choose tasklet or workqueue.

You can use sysctl or driver parameter to decide to use tasklet or 
workqueue.

And finally the Macros like #if ... #else ... #endif also acts as a method.

Zhu Yanjun

>
>> I'm in favor of removing all uses of the tasklet mechanism because of
>> the disadvantages of that mechanism. See also:
>> * "Eliminating tasklets" (https://lwn.net/Articles/239633/).
>> * "Modernizing the tasklet API" (https://lwn.net/Articles/830964/).
>> * Sebastian Andrzej Siewior's opinion about tasklets
>> (https://lore.kernel.org/all/YvovfXMJQAUBsvBZ@linutronix.de/).
> I am also in favor of using workqueues alone not only because of the
> disadvantages above but also to avoid complexity. I would like to know
> if there is anybody who will bothered by the change especially in terms
> of performance.
>
> Thanks,
> Daisuke
>
>> Thanks,
>>
>> Bart.