linux-kernel - Re: [PATCH 11/32] nohz/cpuset: Don't turn off the tick if rcu needs it

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Message-ID: <CAOtvUMeF4aB+1dHOGYvsp+VP+VK_TFEnagVpVvkbBTi50m_=nA@mail.gmail.com>
Date:	Wed, 28 Mar 2012 14:41:42 +0200
From:	Gilad Ben-Yossef <gilad@...yossef.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Christoph Lameter <cl@...ux.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linaro-sched-sig@...ts.linaro.org,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Geoff Levand <geoff@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Zen Lin <zen@...nhuawei.org>
Subject: Re: [PATCH 11/32] nohz/cpuset: Don't turn off the tick if rcu needs it

On Wed, Mar 28, 2012 at 2:21 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> On Wed, Mar 28, 2012 at 09:55:37AM +0200, Gilad Ben-Yossef wrote:
|
>> At the risk of butting in on this little flame war, I think it is
>> worth mentioning
>> that this discussion arouse in the context of of a feature
>> (cpuset/nohz) that deals
>> with a single task running alone on a CPU and making zero use of
>> kernel services,
>> from scheduling, through interrupts, to system calls. It's just a pure
>> 100% cpu  bound task.
>
> Note that cpu isolation is a specific usecase of nohz cpusets. But it's
> intended to be more generally useful (probably for most workloads). That
> means we really want to support syscalls, interrupts and everything. That's
> why it is called adaptive tickless and not just userspace isolated tickless.

Point taken.  I guess I suffer from myopic vision just like the next guy  :-)

Gilad

-- 
Gilad Ben-Yossef
Chief Coffee Drinker
gilad@...yossef.com
Israel Cell: +972-52-8260388
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