Re: [PATCH] net: add support for threaded NAPI polling

[Sebastian Gottschall <s.gottschall@dd-wrt.com>]

Am 30.07.2020 um 17:42 schrieb David Laight:
> From: Sebastian Gottschall
>> Sent: 30 July 2020 15:30
> ...
>>> Quite frankly, I do believe this STATE_THREADED status should be a generic NAPI attribute
>>> that can be changed dynamically, at admin request, instead of having to change/recompile
>>> a driver.
>> thats not that easy. wifi devices do use dummy netdev devices. they are
>> not visible to sysfs and other administrative options.
>> so changing it would just be possible if a special mac80211 based
>> control would be implemented for these drivers.
>> for standard netdev devices it isnt a big thing to implement a
>> administrative control by sysfs (if you are talking about such a feature)
> ISTM that a global flag that made all NAPI callbacks be made
> from a worker thread rather than softint would be more approriate.
> Or even something that made the softint callbacks themselves
> only run an a specific high(ish) priority kernel thread.
>
> While it might slow down setups that need very low ethernet
> latency it will help those that don't want application RT threads
> to be 'stolen' by the softint code while they hold application
> mutex or are waiting to be woken by a cv.
this will not work either. i already identified drivers which are 
incompatible with that approach. (marvell mvneta for instance)
so threading should be a feature which should be enabled or disabled on 
known working chipsets. but it cannot be used as
set and forget feature for everything unless the specific driver are fixed.
>
> 	David
>
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