linux-kernel - Re: [RFC][PATCH v2] sched/rt: Use IPI to trigger RT task push migration instead of pulling

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Message-ID: <20150226074609.27ccd39d@grimm.local.home>
Date:	Thu, 26 Feb 2015 07:46:09 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <williams@...hat.com>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jörn Engel <joern@...estorage.com>
Subject: Re: [RFC][PATCH v2] sched/rt: Use IPI to trigger RT task push
 migration instead of pulling

On Thu, 26 Feb 2015 08:49:07 +0100
Peter Zijlstra <peterz@...radead.org> wrote:
 
> Yes, notice that we don't start iterating at the beginning; this in on
> purpose. If we start iterating at the beginning, _every_ cpu will again
> pile up on the first one.
> 
> By starting at the current cpu, each cpu will start iteration some place
> else and hopefully, with a big enough system, different CPUs end up on a
> different rto cpu.

Note, v3 doesn't start at the current CPU, it starts at the original
CPU again. As the start of every IPI comes from a different CPU, this
still keeps a restart from clobbering the same CPU.

-- Steve
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