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From: David Miller <davem@davemloft.net>
To: pabeni@redhat.com
Cc: frederic@kernel.org, linux-kernel@vger.kernel.org,
	alexander.levin@verizon.com, peterz@infradead.org,
	mchehab@s-opensource.com, torvalds@linux-foundation.org,
	hannes@stressinduktion.org, paulmck@linux.vnet.ibm.com,
	wanpeng.li@hotmail.com, dima@arista.com, tglx@linutronix.de,
	akpm@linux-foundation.org, rrendec@arista.com, mingo@kernel.org,
	sgruszka@redhat.com, riel@redhat.com, edumazet@google.com
Subject: Re: [RFC PATCH 0/4] softirq: Per vector threading v3
Date: Tue, 23 Jan 2018 11:22:01 -0500 (EST)	[thread overview]
Message-ID: <20180123.112201.1263563609292212852.davem@davemloft.net> (raw)
In-Reply-To: <1516702432.2554.37.camel@redhat.com>

From: Paolo Abeni <pabeni@redhat.com>
Date: Tue, 23 Jan 2018 11:13:52 +0100

> Hi,
> 
> On Fri, 2018-01-19 at 16:46 +0100, Frederic Weisbecker wrote:
>> As per Linus suggestion, this take doesn't limit the number of occurences
>> per jiffy anymore but instead defers a vector to workqueues as soon as
>> it gets re-enqueued on IRQ tail.
>> 
>> No tunable here, so testing should be easier.
>> 
>> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
>> 	softirq/thread-v3
>> 
>> HEAD: 6835e92cbd70ef4a056987d2e1ed383b294429d4
> 
> I tested this series in the UDP flood scenario, binding the user space
> process receiving the packets on the same CPU processing the related
> IRQ, and the tput sinks nearly to 0, like before Eric's patch.
> 
> The perf tool says that almost all the softirq processing is done
> inside the workqueue, but the user space process is scheduled very
> rarely, while before this series, in this scenario, ksoftirqd and the
> user space process got a fair share of the CPU time.

Do workqueue threads get a higher scheduling priority than user
processes?  If so, that's going to work against the entire point of
deferring softirq work into a thread.

Or is it that the workqueue execution is simply not yielding for some
reason?

  parent reply	other threads:[~2018-01-23 16:22 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-19 15:46 [RFC PATCH 0/4] softirq: Per vector threading v3 Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 1/4] softirq: Limit vector to a single iteration on IRQ tail Frederic Weisbecker
2018-01-19 16:16   ` David Miller
2018-01-19 18:25     ` Linus Torvalds
2018-01-19 18:47       ` David Miller
2018-01-21 16:30         ` Frederic Weisbecker
2018-01-21 16:57           ` David Miller
2018-01-19 15:46 ` [RFC PATCH 2/4] softirq: Per vector deferment to workqueue Frederic Weisbecker
2018-01-20  8:41   ` Pavan Kondeti
2018-01-21 16:11     ` Frederic Weisbecker
2018-01-21 17:50       ` Pavan Kondeti
2018-01-21 20:48         ` Frederic Weisbecker
2018-02-08 17:44   ` Sebastian Andrzej Siewior
2018-02-08 18:45     ` David Miller
2018-02-08 20:14       ` Dmitry Safonov
2018-02-08 20:22         ` David Miller
2018-02-08 20:30           ` Dmitry Safonov
2018-02-09  4:11             ` Mike Galbraith
2018-02-09 12:35               ` Sebastian Andrzej Siewior
2018-02-15 16:13     ` Frederic Weisbecker
2018-02-15 16:58       ` Sebastian Andrzej Siewior
2018-01-19 15:46 ` [RFC PATCH 3/4] softirq: Defer to workqueue when rescheduling is needed Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 4/4] softirq: Replace ksoftirqd with workqueues entirely Frederic Weisbecker
2018-01-22 19:58 ` [RFC PATCH 0/4] softirq: Per vector threading v3 Mauro Carvalho Chehab
2018-01-23 10:13 ` Paolo Abeni
2018-01-23 12:32   ` Dmitry Safonov
2018-01-24  2:12     ` Frederic Weisbecker
2018-01-23 16:22   ` David Miller [this message]
2018-01-23 16:57     ` Paolo Abeni
2018-01-23 17:42       ` Linus Torvalds
2018-01-23 18:01         ` Mike Galbraith
2018-01-23 18:24         ` David Miller
2018-01-24  1:57           ` Frederic Weisbecker
2018-01-24  2:01             ` Frederic Weisbecker
2018-01-24 14:54         ` Paolo Abeni
2018-01-24 15:05           ` David Miller
2018-01-24 16:11             ` Paolo Abeni
2018-02-07 14:18 ` Mauro Carvalho Chehab
2018-03-01 15:21   ` Frederic Weisbecker

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