doubt on schedule_work() - work task getting scheduled lately

[Muni Sekhar]

On Fri, Jul 29, 2016 at 9:05 PM, Daniel. <danielhilst at gmail.com> wrote:
> Nice tool @Ricardo!
>
> 2016-07-29 10:48 GMT-03:00 Ricardo Ribalda Delgado <ricardo.ribalda at gmail.com>:
>> you can use http://lttng.org/ for analyzing this
Thanks Ricardo, I will use this.

>>
>> Regards!
>>
>> On Fri, Jul 29, 2016 at 12:44 PM, Pranay Srivastava <pranjas at gmail.com> wrote:
>>> On Fri, Jul 29, 2016 at 4:02 PM, Muni Sekhar <munisekharrms at gmail.com> wrote:
>>>> Hi All,
>>>>
>>>> I have a doubt regarding the workqueue scheduling.
>>>>
>>>> I am using the workqueue for processing the Rx Interrupt data. I am
>>>> calling schedule_work() on receiving the Rx interrupt from hardware.
>>>>
>>>> I calculated the time between calling the schedule_work() and
>>>> workqueue task actually getting executed, Here I see many cases of
>>>> less than 100 us(It is fairly good).
>>>>
>>>> But sometimes I see 10’s of ms and a lot in the 100’s of ms. I have
>>>> seen over 0.5 secs too. I would like to know why does sometimes kernel
>>>> takes longer time(in milli seconds) to schedule it? Is there any way
>>>> to reduce this time gap?
>>>>
>>>>
>>>> My code:
>>>>
>>>> static void my_workqueuetask(struct work_struct *work)
>>>> {
>>>>     printk("In %s() \n",__func__);
>>>>
>>> You probably don't need this if it's just for your work_fn, yeah but
>>> if there's race between this and something else...
>>>>     mutex_lock(&bh_mutex);
>>>>
>>>>     //Do something here
>>>>
>>>>     mutex_unlock(&bh_mutex);
>>>> }
>>>>
>>>>
>>>> static irqreturn_t my_irq_handler(int irq, void *dev)
>>>> {
>>>>         ……;
>>>>
>>>>         if(Rx Interrupt)
>>>>              schedule_work(&rx_work);
>>>
>>> Maybe system_wq has too much already on it's plate?
>>> Have you tried the same with completion and a kthread? or
>>> with your own workqueue, overkill but you can give it a shot.
I have not tried this. First I will analyze with lttng and then
attempts this. Does using our own workqueue reduces the latency?

>>>>
>>>> return IRQ_HANDLED;
>>>> }
>>>>
>>>> --
>>>> Thanks,
>>>> Sekhar
>>>>
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>>>> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>>
>>>
>>> --
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>>>
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>>
>>
>>
>> --
>> Ricardo Ribalda
>>
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>
>
>
> --
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-- 
Thanks,
Sekhar