On Fri, Jul 29, 2016 at 9:05 PM, Daniel. [off-list ref] wrote:

Nice tool @Ricardo!

2016-07-29 10:48 GMT-03:00 Ricardo Ribalda Delgado [off-list ref]:

quoted

you can use http://lttng.org/ for analyzing this

Thanks Ricardo, I will use this.

quoted

Regards!

On Fri, Jul 29, 2016 at 12:44 PM, Pranay Srivastava [off-list ref] wrote:

quoted

On Fri, Jul 29, 2016 at 4:02 PM, Muni Sekhar [off-list ref] wrote:

quoted

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...

quoted

    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?

quoted

quoted

quoted

return IRQ_HANDLED;
}

--
Thanks,
Sekhar

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Ricardo Ribalda

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Thanks,
Sekhar