linux-kernel - Re: [PATCH 5/8] nohz: Restart the tick from irq exit

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Message-ID: <20150612130615.GB29736@lerouge>
Date:	Fri, 12 Jun 2015 15:06:16 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Ingo Molnar <mingo@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 5/8] nohz: Restart the tick from irq exit

On Fri, Jun 12, 2015 at 02:59:41PM +0200, Peter Zijlstra wrote:
> On Fri, Jun 12, 2015 at 02:38:36PM +0200, Frederic Weisbecker wrote:
> > On Fri, Jun 12, 2015 at 09:32:45AM +0200, Peter Zijlstra wrote:
> > > On Thu, Jun 11, 2015 at 07:36:05PM +0200, Frederic Weisbecker wrote:
> > > > Restart the tick when necessary from the irq exit path. It makes nohz
> > > > full more flexible and allow it to piggyback the tick restart on the
> > > > scheduler IPI in the future instead of sending a dedicated IPI that
> > > > often doubles the scheduler IPI on task wakeup. This will require
> > > > careful review of resched_curr() callers.
> > > 
> > > This seems to assume schedule_ipi() callers use irq_exit(), this is
> > > false.
> > 
> > Indeed there will be that too. Note the current patch doesn't yet rely on
> > schedule_ipi(), we are still using the nohz ipis.
> 
> Ah, then I just didn't understand your changelog right.

I think I should make it clearer, I must admit it's a bit confused :)
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