When to use threaded interrupts?

[Kosta Zertsekel]

​>> I think I get the pro of using threaded interrupts - to decrease the
maximum
>> interrupt latency on RT workloads and/or RT machines (servers, embedded,
>> etc.).
​>> So, I'd like to ask:
>>    - Why not **all** of the drivers use the threaded interrupts?
>>    - What are the cons of the threaded interrupts?
>>
> Just a wild assumption: maybe the cost of incurring context switches ?
> (comparing to tasklets)

I get that threaded IRQ is better than softIrqs because threaded IRQ
supports
priorities. On the other hand, added context switches surely get system
slower.
But from the practical point of view - why on relatively new Intel PC there
are
no threaded irqs at all?

```
$ uname -a
Linux kostaz-OptiPlex-7010 3.19.0-26-generic #28-Ubuntu SMP Tue Aug 11
14:16:32 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
```

--- KostaZ

On Thu, Sep 10, 2015 at 11:09 PM, Rami Rosen <roszenrami at gmail.com> wrote:

> Kosta,
>
> ​​
> Just a wild assumption: maybe the cost of incurring context switches ?
> (comparing to tasklets)
>
> Best Regards,
> Rami Rosen
> http://ramirose.wix.com/ramirosen
>
>
>
> On 10 September 2015 at 20:49, Kosta Zertsekel <zertsekel at gmail.com>
> wrote:
> > Hi guys,
> >
> > I hope I'm on right mailing list. :-)
> > I think I get the pro of using threaded interrupts - to decrease the
> maximum
> > interrupt latency on RT workloads and/or RT machines (servers, embedded,
> > etc.).
> >
> > Also, I see that in 4.2 there are only ~76 drivers that use threaded
> > interrupt:
> > ```
> > $ git grep -l IRQ_WAKE_THREAD | sort | grep -v "\.h" | wc -l
> > 76
> > ```
> >
> ​​
> > So, I'd like to ask:
> >    - Why not **all** of the drivers use the threaded interrupts?
> >    - What are the cons of the threaded interrupts?
> >
> > Thanks,
> > --- KostaZ
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
>
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