From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from m43-7.mailgun.net ([69.72.43.7]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k0Swj-0008Ip-6e for ath10k@lists.infradead.org; Tue, 28 Jul 2020 16:59:26 +0000 From: "Rakesh Pillai" References: <1595351666-28193-1-git-send-email-pillair@codeaurora.org> <20200721172514.GT1339445@lunn.ch> <20200725081633.7432-1-hdanton@sina.com> <8359a849-2b8a-c842-a501-c6cb6966e345@dd-wrt.com> <20200725145728.10556-1-hdanton@sina.com> <2664182a-1d03-998d-8eff-8478174a310a@dd-wrt.com> In-Reply-To: Subject: RE: [RFC 0/7] Add support to process rx packets in thread Date: Tue, 28 Jul 2020 22:29:02 +0530 Message-ID: <001001d66500$69a58970$3cf09c50$@codeaurora.org> MIME-Version: 1.0 Content-Language: en-us List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: 'David Laight' , 'Sebastian Gottschall' , 'Hillf Danton' Cc: 'Andrew Lunn' , netdev@vger.kernel.org, linux-wireless@vger.kernel.org, dianders@chromium.org, ath10k@lists.infradead.org, linux-kernel@vger.kernel.org, 'Markus Elfring' , evgreen@chromium.org, kuba@kernel.org, johannes@sipsolutions.net, davem@davemloft.net, kvalo@codeaurora.org > -----Original Message----- > From: David Laight > Sent: Sunday, July 26, 2020 4:46 PM > To: 'Sebastian Gottschall' ; Hillf Danton > > Cc: Andrew Lunn ; Rakesh Pillai ; > netdev@vger.kernel.org; linux-wireless@vger.kernel.org; linux- > kernel@vger.kernel.org; ath10k@lists.infradead.org; > dianders@chromium.org; Markus Elfring ; > evgreen@chromium.org; kuba@kernel.org; johannes@sipsolutions.net; > davem@davemloft.net; kvalo@codeaurora.org > Subject: RE: [RFC 0/7] Add support to process rx packets in thread > > From: Sebastian Gottschall > > 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) _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k