From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, Jakub Kicinski <kuba@kernel.org>
Cc: jstultz@google.com, edumazet@google.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] softirq: don't yield if only expedited handlers are pending
Date: Fri, 03 Mar 2023 12:41:27 +0100 [thread overview]
Message-ID: <87sfemjc48.ffs@tglx> (raw)
In-Reply-To: <Y7viEa4BC3yJRXIS@hirez.programming.kicks-ass.net>
On Mon, Jan 09 2023 at 10:44, Peter Zijlstra wrote:
> On Thu, Dec 22, 2022 at 02:12:44PM -0800, Jakub Kicinski wrote:
>> Tweak the need_resched() condition to be ignored if all pending
>> softIRQs are "non-deferred". The tasklet would run relatively
>> soon, anyway, but once ksoftirqd is woken we're risking stalls.
>>
>> I did not see any negative impact on the latency in an RR test
>> on a loaded machine with this change applied.
>
> Ignoring need_resched() will get you in trouble with RT people real
> fast.
In this case not really. softirq processing is preemptible in RT, but
it's still a major pain ...
Thanks,
tglx
next prev parent reply other threads:[~2023-03-03 11:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-22 22:12 [PATCH 0/3] softirq: uncontroversial change Jakub Kicinski
2022-12-22 22:12 ` [PATCH 1/3] softirq: rename ksoftirqd_running() -> ksoftirqd_should_handle() Jakub Kicinski
2022-12-22 22:12 ` [PATCH 2/3] softirq: avoid spurious stalls due to need_resched() Jakub Kicinski
2023-01-31 22:32 ` Jakub Kicinski
2023-03-03 13:30 ` Thomas Gleixner
2023-03-03 15:18 ` Thomas Gleixner
2023-03-03 21:31 ` Jakub Kicinski
2023-03-03 22:37 ` Paul E. McKenney
2023-03-03 23:25 ` Dave Taht
2023-03-04 1:14 ` Paul E. McKenney
2023-03-03 23:36 ` Paul E. McKenney
2023-03-03 23:44 ` Jakub Kicinski
2023-03-04 1:25 ` Paul E. McKenney
2023-03-04 1:39 ` Jakub Kicinski
2023-03-04 3:11 ` Paul E. McKenney
2023-03-04 20:48 ` Paul E. McKenney
2023-03-05 20:43 ` Thomas Gleixner
2023-03-05 22:42 ` Paul E. McKenney
2023-03-05 23:00 ` Frederic Weisbecker
2023-03-06 4:30 ` Paul E. McKenney
2023-03-06 11:22 ` Frederic Weisbecker
2023-03-06 9:13 ` David Laight
2023-03-06 11:57 ` Frederic Weisbecker
2023-03-06 14:57 ` Paul E. McKenney
2023-03-07 0:51 ` Jakub Kicinski
2022-12-22 22:12 ` [PATCH 3/3] softirq: don't yield if only expedited handlers are pending Jakub Kicinski
2023-01-09 9:44 ` Peter Zijlstra
2023-01-09 10:16 ` Eric Dumazet
2023-01-09 19:12 ` Jakub Kicinski
2023-03-03 11:41 ` Thomas Gleixner [this message]
2023-03-03 14:17 ` Thomas Gleixner
2023-04-20 17:24 ` [PATCH 0/3] softirq: uncontroversial change Paolo Abeni
2023-04-20 17:41 ` Eric Dumazet
2023-04-20 20:23 ` Paolo Abeni
2023-04-21 2:48 ` Jason Xing
2023-04-21 9:33 ` Paolo Abeni
2023-04-21 9:46 ` Jason Xing
2023-05-09 19:56 ` [tip: irq/core] Revert "softirq: Let ksoftirqd do its job" tip-bot2 for Paolo Abeni
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