> -----Original Message----- > From: David Laight <David.Laight@xxxxxxxxxx> > Sent: Sunday, July 26, 2020 4:46 PM > To: 'Sebastian Gottschall' <s.gottschall@xxxxxxxxxx>; Hillf Danton > <hdanton@xxxxxxxx> > Cc: Andrew Lunn <andrew@xxxxxxx>; Rakesh Pillai <pillair@xxxxxxxxxxxxxx>; > netdev@xxxxxxxxxxxxxxx; linux-wireless@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; ath10k@xxxxxxxxxxxxxxxxxxx; > dianders@xxxxxxxxxxxx; Markus Elfring <Markus.Elfring@xxxxxx>; > evgreen@xxxxxxxxxxxx; kuba@xxxxxxxxxx; johannes@xxxxxxxxxxxxxxxx; > davem@xxxxxxxxxxxxx; kvalo@xxxxxxxxxxxxxx > Subject: RE: [RFC 0/7] Add support to process rx packets in thread > > From: Sebastian Gottschall <s.gottschall@xxxxxxxxxx> > > Sent: 25 July 2020 16:42 > > >> i agree. i just can say that i tested this patch recently due this > > >> discussion here. and it can be changed by sysfs. but it doesnt work for > > >> wifi drivers which are mainly using dummy netdev devices. for this i > > >> made a small patch to get them working using napi_set_threaded > manually > > >> hardcoded in the drivers. (see patch bellow) > > > > By CONFIG_THREADED_NAPI, there is no need to consider what you did > here > > > in the napi core because device drivers know better and are responsible > > > for it before calling napi_schedule(n). > > > yeah. but that approach will not work for some cases. some stupid > > drivers are using locking context in the napi poll function. > > in that case the performance will runto shit. i discovered this with the > > mvneta eth driver (marvell) and mt76 tx polling (rx works) > > for mvneta is will cause very high latencies and packet drops. for mt76 > > it causes packet stop. doesnt work simply (on all cases no crashes) > > so the threading will only work for drivers which are compatible with > > that approach. it cannot be used as drop in replacement from my point of > > view. > > its all a question of the driver design > > Why should it make (much) difference whether the napi callbacks (etc) > are done in the context of the interrupted process or that of a > specific kernel thread. > The process flags (or whatever) can even be set so that it appears > to be the expected 'softint' context. > > In any case running NAPI from a thread will just show up the next > piece of code that runs for ages in softint context. > I think I've seen the tail end of memory being freed under rcu > finally happening under softint and taking absolutely ages. > > David > Hi All, Is the threaded NAPI change posted to kernel ? Is the conclusion of this discussion that " we cannot use threads for processing packets " ?? > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, > MK1 1PT, UK > Registration No: 1397386 (Wales)
