linux-kernel - Re: [EXT] Re: [PATCH v4 03/13] task_isolation: userspace hard isolation from kernel

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Message-ID: <98978b81e7eda04c256c3d837c36a032f5d475fb.camel@marvell.com>
Date:   Sat, 17 Oct 2020 01:13:17 +0000
From:   Alex Belits <abelits@...vell.com>
To:     "frederic@...nel.org" <frederic@...nel.org>,
        "nitesh@...hat.com" <nitesh@...hat.com>
CC:     "mingo@...nel.org" <mingo@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        Prasun Kapoor <pkapoor@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH v4 03/13] task_isolation: userspace hard
 isolation from kernel


On Tue, 2020-10-06 at 12:35 +0200, Frederic Weisbecker wrote:
> On Mon, Oct 05, 2020 at 02:52:49PM -0400, Nitesh Narayan Lal wrote:
> > On 10/4/20 7:14 PM, Frederic Weisbecker wrote:
> > > On Sun, Oct 04, 2020 at 02:44:39PM +0000, Alex Belits wrote:
> > > 
> > > > The idea behind this is that isolation breaking events are
> > > > supposed to
> > > > be known to the applications while applications run normally,
> > > > and they
> > > > should not require any analysis or human intervention to be
> > > > handled.
> > > Sure but you can use trace events for that. Just trace
> > > interrupts, workqueues,
> > > timers, syscalls, exceptions and scheduler events and you get all
> > > the local
> > > disturbance. You might want to tune a few filters but that's
> > > pretty much it.
> 
> formation,
> > > you can trace the workqueue and timer queue events and just
> > > filter those that
> > > target your isolated CPUs.
> > > 
> > 
> > I agree that we can do all those things with tracing.
> > However, IMHO having a simplified logging mechanism to gather the
> > source of
> > violation may help in reducing the manual effort.
> > 
> > Although, I am not sure how easy will it be to maintain such an
> > interface
> > over time.
> 
> The thing is: tracing is your simplified logging mechanism here. You
> can achieve
> the same in userspace with _way_ less code, no race, and you can do
> it in
> bash.

The idea is that this mechanism should be usable when no one is there
to run things in bash, or no information about what might happen. It
should be able to report rare events in production when users may not
be able to reproduce them.

-- 
Alex