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From: Pavel Machek <pavel@ucw.cz>
To: Alex Belits <abelits@marvell.com>
Cc: "nitesh@redhat.com" <nitesh@redhat.com>,
	"frederic@kernel.org" <frederic@kernel.org>,
	Prasun Kapoor <pkapoor@marvell.com>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"trix@redhat.com" <trix@redhat.com>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"peterx@redhat.com" <peterx@redhat.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"mtosatti@redhat.com" <mtosatti@redhat.com>,
	"will@kernel.org" <will@kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"leon@sidebranch.com" <leon@sidebranch.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"pauld@redhat.com" <pauld@redhat.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH v5 0/9] "Task_isolation" mode
Date: Sat, 5 Dec 2020 21:40:49 +0100	[thread overview]
Message-ID: <20201205204049.GA8578@amd> (raw)
In-Reply-To: <8d887e59ca713726f4fcb25a316e1e932b02823e.camel@marvell.com>

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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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WARNING: multiple messages have this Message-ID (diff)
From: Pavel Machek <pavel@ucw.cz>
To: Alex Belits <abelits@marvell.com>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"nitesh@redhat.com" <nitesh@redhat.com>,
	"pauld@redhat.com" <pauld@redhat.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"frederic@kernel.org" <frederic@kernel.org>,
	"mtosatti@redhat.com" <mtosatti@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"leon@sidebranch.com" <leon@sidebranch.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"peterx@redhat.com" <peterx@redhat.com>,
	"trix@redhat.com" <trix@redhat.com>,
	Prasun Kapoor <pkapoor@marvell.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"will@kernel.org" <will@kernel.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v5 0/9] "Task_isolation" mode
Date: Sat, 5 Dec 2020 21:40:49 +0100	[thread overview]
Message-ID: <20201205204049.GA8578@amd> (raw)
In-Reply-To: <8d887e59ca713726f4fcb25a316e1e932b02823e.camel@marvell.com>


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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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  parent reply	other threads:[~2020-12-05 20:41 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-23 17:42 [PATCH v5 0/9] "Task_isolation" mode Alex Belits
2020-11-23 17:42 ` Alex Belits
2020-11-23 17:56 ` [PATCH v5 1/9] task_isolation: vmstat: add quiet_vmstat_sync function Alex Belits
2020-11-23 17:56   ` Alex Belits
2020-11-23 21:48   ` Thomas Gleixner
2020-11-23 21:48     ` Thomas Gleixner
2020-11-23 17:56 ` [PATCH v5 2/9] task_isolation: vmstat: add vmstat_idle function Alex Belits
2020-11-23 17:56   ` Alex Belits
2020-11-23 21:49   ` Thomas Gleixner
2020-11-23 21:49     ` Thomas Gleixner
2020-11-23 17:56 ` [PATCH v5 3/9] task_isolation: userspace hard isolation from kernel Alex Belits
2020-11-23 17:56   ` Alex Belits
2020-11-23 22:01   ` Thomas Gleixner
2020-11-23 22:01     ` Thomas Gleixner
2020-11-23 17:57 ` [PATCH v5 4/9] task_isolation: Add task isolation hooks to arch-independent code Alex Belits
2020-11-23 17:57   ` Alex Belits
2020-11-23 22:31   ` Thomas Gleixner
2020-11-23 22:31     ` Thomas Gleixner
2020-11-23 17:57 ` [PATCH v5 5/9] task_isolation: Add driver-specific hooks Alex Belits
2020-11-23 17:57   ` Alex Belits
2020-12-02 14:18   ` Mark Rutland
2020-12-02 14:18     ` Mark Rutland
2020-12-04  0:43     ` [EXT] " Alex Belits
2020-12-04  0:43       ` Alex Belits
2020-11-23 17:58 ` [PATCH v5 6/9] task_isolation: arch/arm64: enable task isolation functionality Alex Belits
2020-11-23 17:58   ` Alex Belits
2020-12-02 13:59   ` Mark Rutland
2020-12-02 13:59     ` Mark Rutland
2020-12-04  0:37     ` [EXT] " Alex Belits
2020-12-04  0:37       ` Alex Belits
2020-12-07 11:57       ` Mark Rutland
2020-12-07 11:57         ` Mark Rutland
2020-11-23 17:58 ` [PATCH v5 7/9] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu() Alex Belits
2020-11-23 17:58   ` Alex Belits
2020-11-23 22:13   ` Frederic Weisbecker
2020-11-23 22:13     ` Frederic Weisbecker
2020-11-23 22:35     ` Alex Belits
2020-11-23 22:35       ` Alex Belits
2020-11-23 22:36   ` Thomas Gleixner
2020-11-23 22:36     ` Thomas Gleixner
2020-12-02 14:20   ` Mark Rutland
2020-12-02 14:20     ` Mark Rutland
2020-12-04  0:54     ` [EXT] " Alex Belits
2020-12-04  0:54       ` Alex Belits
2020-12-07 11:58       ` Mark Rutland
2020-12-07 11:58         ` Mark Rutland
2020-11-23 17:58 ` [PATCH v5 8/9] task_isolation: ringbuffer: don't interrupt CPUs running isolated tasks on buffer resize Alex Belits
2020-11-23 17:58   ` Alex Belits
2020-11-23 17:58 ` [PATCH v5 9/9] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Alex Belits
2020-11-23 17:58   ` Alex Belits
2020-11-23 22:29   ` Frederic Weisbecker
2020-11-23 22:29     ` Frederic Weisbecker
2020-11-23 22:39     ` [EXT] " Alex Belits
2020-11-23 22:39       ` Alex Belits
2020-11-23 23:21       ` Frederic Weisbecker
2020-11-23 23:21         ` Frederic Weisbecker
2020-11-25  3:20         ` Alex Belits
2020-11-25  3:20           ` Alex Belits
2021-01-22 15:00         ` Marcelo Tosatti
2021-01-22 15:00           ` Marcelo Tosatti
2020-11-24 16:36 ` [PATCH v5 0/9] "Task_isolation" mode Tom Rix
2020-11-24 16:36   ` Tom Rix
2020-11-24 17:40   ` [EXT] " Alex Belits
2020-11-24 17:40     ` Alex Belits
2020-12-02 14:02     ` Mark Rutland
2020-12-02 14:02       ` Mark Rutland
2020-12-04  0:39       ` Alex Belits
2020-12-04  0:39         ` Alex Belits
2020-12-05 20:40 ` Pavel Machek [this message]
2020-12-05 20:40   ` Pavel Machek
2020-12-05 23:25   ` Thomas Gleixner
2020-12-05 23:25     ` Thomas Gleixner
2020-12-11 18:08     ` Yury Norov
2020-12-11 18:08       ` Yury Norov

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