From: David Miller <davem@davemloft.net>
To: torvalds@linux-foundation.org
Cc: pabeni@redhat.com, frederic@kernel.org,
linux-kernel@vger.kernel.org, alexander.levin@verizon.com,
peterz@infradead.org, mchehab@s-opensource.com,
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 13:24:24 -0500 (EST) [thread overview]
Message-ID: <20180123.132424.1035340800864767853.davem@davemloft.net> (raw)
In-Reply-To: <CA+55aFwEMe=jV7pvV2dWFKrQ--mAw3buXhdJ-Qk2u-290rTQQQ@mail.gmail.com>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 23 Jan 2018 09:42:32 -0800
> But I wonder if the test triggers the "lets run lots of workqueue
> threads", and then the single-threaded user space just gets blown out
> of the water by many kernel threads. Each thread gets its own "fair"
> amount of CPU, but..
If a single cpu's softirq deferral can end up running on multiple
workqueue threads, indeed that's a serious problem.
So if we're in a workqueue and it does a:
schedule_work_on(this_cpu, currently_executing_work);
it'll potentially make a new thread?
That's exactly the code path that will get exercised during a UDP
flood the way that vector_work_func() is implemented.
next prev parent reply other threads:[~2018-01-23 18:24 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
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 [this message]
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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