From: Dmitry Safonov <dima@arista.com>
To: Frederic Weisbecker <frederic@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>,
LKML <linux-kernel@vger.kernel.org>,
Levin Alexander <alexander.levin@verizon.com>,
Peter Zijlstra <peterz@infradead.org>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Wanpeng Li <wanpeng.li@hotmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Eric Dumazet <edumazet@google.com>,
Radu Rendec <rrendec@arista.com>, Ingo Molnar <mingo@kernel.org>,
Stanislaw Gruszka <sgruszka@redhat.com>,
Paolo Abeni <pabeni@redhat.com>, Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Miller <davem@davemloft.net>
Subject: Re: [RFC PATCH 0/5] softirq: Per vector threading v2
Date: Thu, 18 Jan 2018 12:44:08 +0000 [thread overview]
Message-ID: <1516279448.2762.7.camel@arista.com> (raw)
In-Reply-To: <20180118040916.GA25885@lerouge>
On Thu, 2018-01-18 at 05:09 +0100, Frederic Weisbecker wrote:
> On Wed, Jan 17, 2018 at 07:09:39PM -0800, Linus Torvalds wrote:
> > It should never trigger under any normal load, but I think it
> > *should*
> > trigger under the load that the networking people worry about. If
> > you
> > get a flood of UDP packets, and spend a lot of time in softirqs,
> > I'm
> > pretty sure you'd hit that case of seeing the same softirq re-
> > raised
> > fairly naturally and quickly.
>
> Ok after a quick tracing check, it seems that executing the same
> softirq
> vector twice in the same interrupt does not happen without much
> stress.
Uhm, yes it should.. but that was what I originally saw on hw - that
raising a new softirq under UDP packet storm might happen slower than
expected. And a new softirq is raised only after the first one was
processed. Which results in rare deferring.
--
Dima
prev parent reply other threads:[~2018-01-18 12:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-16 4:40 [RFC PATCH 0/5] softirq: Per vector threading v2 Frederic Weisbecker
2018-01-16 4:40 ` [RFC PATCH 1/5] softirq: Account time and iteration stats per vector Frederic Weisbecker
2018-01-16 4:40 ` [RFC PATCH 2/5] softirq: Per vector deferment to workqueue Frederic Weisbecker
2018-01-16 4:40 ` [RFC PATCH 3/5] softirq: Defer to workqueue when rescheduling is needed Frederic Weisbecker
2018-01-16 4:40 ` [RFC PATCH 4/5] softirq: Replace ksoftirqd with workqueues entirely Frederic Weisbecker
2018-01-16 4:40 ` [RFC/OPTIONAL PATCH 5/5] softirq: Reset vector call counter before workqueue completion Frederic Weisbecker
2018-01-17 16:56 ` [RFC PATCH 0/5] softirq: Per vector threading v2 Mauro Carvalho Chehab
2018-01-17 18:07 ` Frederic Weisbecker
2018-01-17 23:56 ` Linus Torvalds
2018-01-18 2:55 ` Frederic Weisbecker
2018-01-18 3:09 ` Linus Torvalds
2018-01-18 4:09 ` Frederic Weisbecker
2018-01-18 12:44 ` Dmitry Safonov [this message]
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