Date:   Thu, 2 Mar 2023 17:53:34 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     David Laight <David.Laight@ACULAB.COM>
Cc:     John Stultz <jstultz@google.com>,
        LKML <linux-kernel@vger.kernel.org>, Wei Wang <wvw@google.com>,
        "Midas Chien" <midaschieh@google.com>,
        Kees Cook <keescook@chromium.org>,
        "Anton Vorontsov" <anton@enomsg.org>,
        "Guilherme G. Piccoli" <gpiccoli@igalia.com>,
        Tony Luck <tony.luck@intel.com>,
        "kernel-team@android.com" <kernel-team@android.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Peter Zijlstra" <peterz@infradead.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH] pstore: Revert pmsg_lock back to a normal mutex
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        <CANDhNCo4ruC4pP+iDe49b3e1nAcWtYQj4bx82+oZhyLFYkdFJQ@mail.gmail.com>
        <20230302152103.2618f1b7@gandalf.local.home>
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On Thu, 2 Mar 2023 22:41:36 +0000
David Laight <David.Laight@ACULAB.COM> wrote:

> I can't help feeing that the RT kernel suffers from the
> same problems if the system is under any kind of load.
> You might get slightly better RT response, but the overall
> amount of 'work' a system can actually do will be lower.

That basically is the definition of an RTOS.

But it's not "slightly better RT responses" what you get is a hell of a lot
better responses, and no unbounded priority inversion.

On some workloads I can still get millisecond latency cases on vanilla
Linux where as with the PREEMPT_RT patch, the same workload is still under
a 100 microseconds.

-- Steve