linux-kernel - Re: sched_core_balance() releasing interrupts with pi

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Message-ID: <YjIY8Ciw7IvKKQCZ@linutronix.de>
Date:   Wed, 16 Mar 2022 18:05:52 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: sched_core_balance() releasing interrupts with pi_lock held

On 2022-03-16 17:18:41 [+0100], To Steven Rostedt wrote:
> on top my problems are gone. Let me do some testing and then I would
> patch unless PeterZ does the yelling :)

so the long irq-off section is latency wise less than optimal. A
testcase went from ~40 to 140us. And then there is this:
| NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
| NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #10!!!

which might be RT-only.
I *think* we want first the buggy part gone and then the latency fixed.

> > > Thanks,
> > > 
> > > -- Steve

Sebastian