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From: "Rakesh Pillai" <pillair@codeaurora.org>
To: "'David Laight'" <David.Laight@ACULAB.COM>,
	"'Sebastian Gottschall'" <s.gottschall@dd-wrt.com>,
	"'Hillf Danton'" <hdanton@sina.com>
Cc: "'Andrew Lunn'" <andrew@lunn.ch>, <netdev@vger.kernel.org>,
	<linux-wireless@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<ath10k@lists.infradead.org>, <dianders@chromium.org>,
	"'Markus Elfring'" <Markus.Elfring@web.de>,
	<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
Date: Tue, 28 Jul 2020 22:29:02 +0530	[thread overview]
Message-ID: <001001d66500$69a58970$3cf09c50$@codeaurora.org> (raw)
In-Reply-To: <cb54c2746a3d4ce695e3bda8b576b40e@AcuMS.aculab.com>



> -----Original Message-----
> From: David Laight <David.Laight@ACULAB.COM>
> Sent: Sunday, July 26, 2020 4:46 PM
> To: 'Sebastian Gottschall' <s.gottschall@dd-wrt.com>; Hillf Danton
> <hdanton@sina.com>
> Cc: Andrew Lunn <andrew@lunn.ch>; Rakesh Pillai <pillair@codeaurora.org>;
> netdev@vger.kernel.org; linux-wireless@vger.kernel.org; linux-
> kernel@vger.kernel.org; ath10k@lists.infradead.org;
> dianders@chromium.org; Markus Elfring <Markus.Elfring@web.de>;
> 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 <s.gottschall@dd-wrt.com>
> > 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)


WARNING: multiple messages have this Message-ID
From: "Rakesh Pillai" <pillair@codeaurora.org>
To: 'David Laight' <David.Laight@ACULAB.COM>,
	'Sebastian Gottschall' <s.gottschall@dd-wrt.com>,
	'Hillf Danton' <hdanton@sina.com>
Cc: 'Andrew Lunn' <andrew@lunn.ch>,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	dianders@chromium.org, ath10k@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	'Markus Elfring' <Markus.Elfring@web.de>,
	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
Date: Tue, 28 Jul 2020 22:29:02 +0530	[thread overview]
Message-ID: <001001d66500$69a58970$3cf09c50$@codeaurora.org> (raw)
In-Reply-To: <cb54c2746a3d4ce695e3bda8b576b40e@AcuMS.aculab.com>



> -----Original Message-----
> From: David Laight <David.Laight@ACULAB.COM>
> Sent: Sunday, July 26, 2020 4:46 PM
> To: 'Sebastian Gottschall' <s.gottschall@dd-wrt.com>; Hillf Danton
> <hdanton@sina.com>
> Cc: Andrew Lunn <andrew@lunn.ch>; Rakesh Pillai <pillair@codeaurora.org>;
> netdev@vger.kernel.org; linux-wireless@vger.kernel.org; linux-
> kernel@vger.kernel.org; ath10k@lists.infradead.org;
> dianders@chromium.org; Markus Elfring <Markus.Elfring@web.de>;
> 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 <s.gottschall@dd-wrt.com>
> > 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)


_______________________________________________
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  reply	other threads:[~2020-07-28 16:59 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21 17:14 Rakesh Pillai
2020-07-21 17:14 ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 1/7] mac80211: Add check for napi handle before WARN_ON Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-22 12:56   ` Johannes Berg
2020-07-22 12:56     ` Johannes Berg
2020-07-23 18:26     ` Rakesh Pillai
2020-07-23 18:26       ` Rakesh Pillai
2020-07-23 20:06       ` Johannes Berg
2020-07-23 20:06         ` Johannes Berg
2020-07-24  6:21         ` Rakesh Pillai
2020-07-24  6:21           ` Rakesh Pillai
2020-07-26 16:19         ` Rakesh Pillai
2020-07-26 16:19           ` Rakesh Pillai
2020-07-30 12:40           ` Johannes Berg
2020-07-30 12:40             ` Johannes Berg
2020-07-21 17:14 ` [RFC 2/7] ath10k: Add support to process rx packet in thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 21:53   ` Rajkumar Manoharan
2020-07-21 21:53     ` Rajkumar Manoharan
2020-07-22 12:27     ` Felix Fietkau
2020-07-22 12:27       ` Felix Fietkau
2020-07-22 12:55       ` Johannes Berg
2020-07-22 12:55         ` Johannes Berg
2020-07-22 13:00         ` Felix Fietkau
2020-07-22 13:00           ` Felix Fietkau
2020-07-23  6:09           ` Rajkumar Manoharan
2020-07-23  6:09             ` Rajkumar Manoharan
2021-03-22 23:57           ` Ben Greear
2021-03-22 23:57             ` Ben Greear
2021-03-23  1:20             ` Brian Norris
2021-03-23  1:20               ` Brian Norris
2021-03-23  3:01               ` Ben Greear
2021-03-23  3:01                 ` Ben Greear
2021-03-23  7:45                 ` Felix Fietkau
2021-03-23  7:45                   ` Felix Fietkau
2021-03-25  9:45                   ` Rakesh Pillai
2021-03-25  9:45                     ` Rakesh Pillai
2021-03-25 10:33                     ` Felix Fietkau
2021-03-25 10:33                       ` Felix Fietkau
2020-07-23 18:25     ` Rakesh Pillai
2020-07-23 18:25       ` Rakesh Pillai
2020-07-24 23:11       ` Jacob Keller
2020-07-24 23:11         ` Jacob Keller
2020-07-21 17:14 ` [RFC 3/7] ath10k: Add module param to enable rx thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 4/7] ath10k: Do not exhaust budget on process tx completion Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 5/7] ath10k: Handle the rx packet processing in thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 6/7] ath10k: Add deliver to stack from thread context Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 7/7] ath10k: Handle rx thread suspend and resume Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-23 23:06   ` Sebastian Gottschall
2020-07-23 23:06     ` Sebastian Gottschall
2020-07-24  6:19     ` Rakesh Pillai
2020-07-24  6:19       ` Rakesh Pillai
2020-07-21 17:25 ` [RFC 0/7] Add support to process rx packets in thread Andrew Lunn
2020-07-21 17:25   ` Andrew Lunn
2020-07-21 18:05   ` Florian Fainelli
2020-07-21 18:05     ` Florian Fainelli
2020-07-23 18:21     ` Rakesh Pillai
2020-07-23 18:21       ` Rakesh Pillai
2020-07-23 19:02       ` Florian Fainelli
2020-07-23 19:02         ` Florian Fainelli
2020-07-24  6:20         ` Rakesh Pillai
2020-07-24  6:20           ` Rakesh Pillai
2020-07-24 22:28           ` Florian Fainelli
2020-07-24 22:28             ` Florian Fainelli
2020-07-22  9:12   ` David Laight
2020-07-22  9:12     ` David Laight
2020-07-25  8:16     ` Hillf Danton
2020-07-25 10:38       ` Sebastian Gottschall
2020-07-25 10:38         ` Sebastian Gottschall
2020-07-25 12:25         ` Hillf Danton
2020-07-25 14:08         ` Sebastian Gottschall
2020-07-25 14:08           ` Sebastian Gottschall
2020-07-25 14:57           ` Hillf Danton
2020-07-25 15:41             ` Sebastian Gottschall
2020-07-25 15:41               ` Sebastian Gottschall
2020-07-26 11:16               ` David Laight
2020-07-26 11:16                 ` David Laight
2020-07-28 16:59                 ` Rakesh Pillai [this message]
2020-07-28 16:59                   ` Rakesh Pillai
2020-07-29  1:34                   ` Hillf Danton
2020-07-25 17:57       ` Felix Fietkau
2020-07-25 17:57         ` Felix Fietkau
2020-07-26  1:22         ` Hillf Danton
2020-07-26  8:10           ` Felix Fietkau
2020-07-26  8:10             ` Felix Fietkau
2020-07-26  8:32             ` Hillf Danton
2020-07-26  8:59               ` Felix Fietkau
2020-07-26  8:59                 ` Felix Fietkau
2020-07-22 16:20   ` Jakub Kicinski
2020-07-22 16:20     ` Jakub Kicinski

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