linux-kernel - Re: [PATCH] pstore: Revert pmsg

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Message-ID: <20230302175334.49abf342@gandalf.local.home>
Date:   Thu, 2 Mar 2023 17:53:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     John Stultz <jstultz@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, Wei Wang <wvw@...gle.com>,
        "Midas Chien" <midaschieh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        "Anton Vorontsov" <anton@...msg.org>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Tony Luck <tony.luck@...el.com>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] pstore: Revert pmsg_lock back to a normal mutex

On Thu, 2 Mar 2023 22:41:36 +0000
David Laight <David.Laight@...LAB.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