netdev - Re: [PATCH net-next 08/11] net: hns3: add interrupt affinity support for misc interrupt

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Date:   Mon, 29 Jul 2019 18:17:02 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        "tanhuazhong@...wei.com" <tanhuazhong@...wei.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "lipeng321@...wei.com" <lipeng321@...wei.com>,
        "yisen.zhuang@...wei.com" <yisen.zhuang@...wei.com>,
        "salil.mehta@...wei.com" <salil.mehta@...wei.com>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 08/11] net: hns3: add interrupt affinity support
 for misc interrupt

On 2019/7/27 7:18, Saeed Mahameed wrote:
> On Thu, 2019-07-25 at 10:05 +0800, Yunsheng Lin wrote:
>> On 2019/7/25 3:24, Saeed Mahameed wrote:
>>> On Wed, 2019-07-24 at 11:18 +0800, Huazhong Tan wrote:
>>>> From: Yunsheng Lin <linyunsheng@...wei.com>
>>>>
> 
> [...]
>>>>
>>>> +static void hclge_irq_affinity_notify(struct irq_affinity_notify
>>>> *notify,
>>>> +				      const cpumask_t *mask)
>>>> +{
>>>> +	struct hclge_dev *hdev = container_of(notify, struct hclge_dev,
>>>> +					      affinity_notify);
>>>> +
>>>> +	cpumask_copy(&hdev->affinity_mask, mask);
>>>> +	del_timer_sync(&hdev->service_timer);
>>>> +	hdev->service_timer.expires = jiffies + HZ;
>>>> +	add_timer_on(&hdev->service_timer, cpumask_first(&hdev-
>>>>> affinity_mask));
>>>> +}
>>>
>>> I don't see any relation between your misc irq vector and &hdev-
>>>> service_timer, to me this looks like an abuse of the irq affinity
>>>> API
>>> to allow the user to move the service timer affinity.
>>
>> Hi, thanks for reviewing.
>>
>> hdev->service_timer is used to schedule the periodic work
>> queue hdev->service_task， we want all the management work
>> queue including hdev->service_task to bind to the same cpu
>> to improve cache and power efficiency, it is better to move
>> service timer affinity according to that.
>>
>> The hdev->service_task is changed to delay work queue in
>> next patch " net: hns3: make hclge_service use delayed workqueue",
>> So the affinity in the timer of the delay work queue is automatically
>> set to the affinity of the delay work queue, we will move the
>> "make hclge_service use delayed workqueue" patch before the
>> "add interrupt affinity support for misc interrupt" patch, so
>> we do not have to set service timer affinity explicitly.
>>
>> Also, There is there work queues(mbx_service_task, service_task,
>> rst_service_task) in the hns3 driver, we plan to combine them
>> to one or two workqueue to improve efficiency and readability.
>>
> 
> So just to make it clear, you have 3 deferred works, 2 are triggered by
> the misc irq and 1 is periodic, you want them all on the same core and
> you want to control their affinity via the irq affinity ? for works #1
> and  #2 you get that for free since the irq is triggering them, but for
> work #3 (the periodic one) you need to manually move it when the irq
> affinity changes.

Yes, You are right.

> 
> I guess i am ok with this, since moving the irq affinity isn't only
> required by the periodic work but also for the other works that the irq
> is actually triggering (so it is not an actual abuse, sort of .. )
> 
> 
>