Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 27 Oct 2020 12:06:11 +0100
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Daniel Wagner <wagi@monom.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-rt-users <linux-rt-users@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Clark Williams <williams@redhat.com>
Subject: Re: [ANNOUNCE] v5.9.1-rt19
Message-ID: <20201027110611.5hvuhsp3sjtcshsl@linutronix.de>
References: <20201024091838.gzhn2dlx2j7xnixg@linutronix.de>
 <20201027093616.5vn6xinmthxulhvx@beryllium.lan>
 <20201027100049.xtkmjqdwkn7zec2f@linutronix.de>
 <20201027102547.y6wop7j2ovzg2tyx@beryllium.lan>
 <20201027102851.gizepjlu4opensqb@linutronix.de>
 <20201027103411.h5ushvwsrovxls5u@beryllium.lan>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20201027103411.h5ushvwsrovxls5u@beryllium.lan>
Precedence: bulk

On 2020-10-27 11:34:11 [+0100], Daniel Wagner wrote:
> On Tue, Oct 27, 2020 at 11:28:51AM +0100, Sebastian Andrzej Siewior wrote:
> > Is it running as a RT task?
> 
> root@c2d:~/rt-tests# ./pi_stress
> Starting PI Stress Test
> Number of thread groups: 1
> Duration of test run: infinite
> Number of inversions per group: unlimited
>      Admin thread SCHED_FIFO priority 4
> 1 groups of 3 threads will be created
>       High thread SCHED_FIFO priority 3
>        Med thread SCHED_FIFO priority 2
>        Low thread SCHED_FIFO priority 1
> 
> It says so, let me double check if those task really run with SCHED_FIFO.

urgh. You wrote pi_stress and I read stress-ng. Okay this explains it.

> > Otherwise it looks that if you throw enough non-RT load on the system,
> > RCU can not catch up which does not sound good.
> 
> I think this is what Clark tried to tell me. If I understood him
> correctly the test tool is not correct though.

a dummy RCU section might help. But otherwise it is correct :/

Sebastian