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SubjectRe: [RFC PATCH 0/2] RT scheduling policies for workqueues
On 28.03.2022 07:39:25, Tejun Heo wrote:
> Hello,
>
> On Mon, Mar 28, 2022 at 12:09:27PM +0200, Marc Kleine-Budde wrote:
> > > Having a kthread per "low-latency" tty instance is something I would
> > > prefer. The kwork corner is an anonymous worker instance and probably
> > > does more harm than good. Especially if it is a knob for everyone which
> > > is used for the wrong reasons and manages to be harmful in the end.
> > > With a special kthread for a particular tty, the thread can be assigned
> > > with the desired priority within the system and ttyS1 can be
> > > distinguished from ttyS0 (and so on). This turned out to be useful in a
> > > few setups over the years.
> >
> > +1
> >
> > The networking subsystem has gone the same/similar way with NAPI. NAPI
> > handling can be switched from the softirq to kernel thread on a per
> > interface basis.
>
> I wonder whether it'd be useful to provide a set of wrappers which can make
> switching between workqueue and kworker easy. Semantics-wise, they're
> already mostly aligned and it shouldn't be too difficult to e.g. make an
> unbounded workqueue be backed by a dedicated kthread_worker instead of
> shared pool depending on a flag, or even allow switching dynamically.

For NAPI a sysfs entry was added to switch to threaded mode:

| 5fdd2f0e5c64 net: add sysfs attribute to control napi threaded mode
| 29863d41bb6e net: implement threaded-able napi poll loop support
| 898f8015ffe7 net: extract napi poll functionality to __napi_poll()

regards,
Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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