netdev - Re: [PATCH v5 0/9] "Task

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Date:   Sat, 5 Dec 2020 21:40:49 +0100
From:   Pavel Machek <pavel@....cz>
To:     Alex Belits <abelits@...vell.com>
Cc:     "nitesh@...hat.com" <nitesh@...hat.com>,
        "frederic@...nel.org" <frederic@...nel.org>,
        Prasun Kapoor <pkapoor@...vell.com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "trix@...hat.com" <trix@...hat.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "mtosatti@...hat.com" <mtosatti@...hat.com>,
        "will@...nel.org" <will@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "leon@...ebranch.com" <leon@...ebranch.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "pauld@...hat.com" <pauld@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v5 0/9] "Task_isolation" mode

Hi!

> General description
> 
> This is the result of development and maintenance of task isolation
> functionality that originally started based on task isolation patch
> v15 and was later updated to include v16. It provided predictable
> environment for userspace tasks running on arm64 processors alongside
> with full-featured Linux environment. It is intended to provide
> reliable interruption-free environment from the point when a userspace
> task enters isolation and until the moment it leaves isolation or
> receives a signal intentionally sent to it, and was successfully used
> for this purpose. While CPU isolation with nohz provides an
> environment that is close to this requirement, the remaining IPIs and
> other disturbances keep it from being usable for tasks that require
> complete predictability of CPU timing.

So... what kind of guarantees does this aim to provide / what tasks it
is useful for?

For real time response, we have other approaches.

If you want to guarantee performnace of the "isolated" task... I don't
see how that works. Other tasks on the system still compete for DRAM
bandwidth, caches, etc...

So... what is the usecase?
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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