linux-kernel - Re: [PATCH v4 1/5] nohz_full: add support for "cpu

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Message-ID: <CALCETrWaBe10u1X+AqYM7TsbguL=aF-TyuN3xjqgR5Cg2=FiAA@mail.gmail.com>
Date:	Mon, 13 Jul 2015 13:40:58 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/5] nohz_full: add support for "cpu_isolated" mode

On Mon, Jul 13, 2015 at 12:57 PM, Chris Metcalf <cmetcalf@...hip.com> wrote:
> The existing nohz_full mode makes tradeoffs to minimize userspace
> interruptions while still attempting to avoid overheads in the
> kernel entry/exit path, to provide 100% kernel semantics, etc.
>
> However, some applications require a stronger commitment from the
> kernel to avoid interruptions, in particular userspace device
> driver style applications, such as high-speed networking code.
>
> This change introduces a framework to allow applications to elect
> to have the stronger semantics as needed, specifying
> prctl(PR_SET_CPU_ISOLATED, PR_CPU_ISOLATED_ENABLE) to do so.
> Subsequent commits will add additional flags and additional
> semantics.

I thought the general consensus was that this should be the default
behavior and that any associated bugs should be fixed.

--Andy
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