linux-kernel - Re: [ANNOUNCE] v5.10-rc2-rt4

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Date:   Thu, 12 Nov 2020 13:39:02 +0100
From:   Daniel Wagner <wagi@...om.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v5.10-rc2-rt4

On Tue, Nov 10, 2020 at 07:05:18PM +0100, Sebastian Andrzej Siewior wrote:
> On 2020-11-09 15:37:03 [+0100], Daniel Wagner wrote:
> > > I've been staring at the code of signaltest on Friday and I might need
> > > to stare longer to figure out what it does.
> > 
> > I hear you. Anyway, I gave the current head a run with lazy preemption
> > disabled as you asked for.
> 
> I just sent a few patches your way regarding signaltest. It should help
> you with tracing. I've been playing with it on a juno box and I didn't
> see anything odd. My max value was below 200us. I added a few tracing
> bits. With sched, signal and hrtimer events you should be able to see
> what delays the RT thread. I didn't see anything odd.

With the current version signaltest + your test patch and 'taskset -c1'
the results looks good again, around 230us (running since 2 hours). I've
tested first without taskset and it took about an half hour to hit
350us. So pinning the threads on one CPU fixes it.

I think we change signaltest to use the correct affinity on
default. Also, I see that sigwaittest has some code for it, but it, but
it would be a good idea to set the defaults so that out of the box the
test does the right thing.

I'm sorry about dragging you into this problem.