linux-kernel - Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging normal ones

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Message-ID: <20150702031529.GB3717@linux.vnet.ibm.com>
Date:	Wed, 1 Jul 2015 20:15:29 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	josh@...htriplett.org, Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	tglx@...utronix.de, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, dvhart@...ux.intel.com, fweisbec@...il.com,
	oleg@...hat.com, bobby.prani@...il.com
Subject: Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging
 normal ones

On Thu, Jul 02, 2015 at 04:50:45AM +0200, Mike Galbraith wrote:
> On Wed, 2015-07-01 at 19:18 -0700, Paul E. McKenney wrote:
> 
> > Does their normal workload trigger the condition that results in the
> > expedited grace period?  If so, do they use NO_HZ_FULL?
> 
> They're having no trouble that I'm aware of, and I definitely would be
> made aware.  They're not currently using a kernel with NO_HZ_FULL even
> built in, as that stuff is far far too raw in the current kernel.
> 
> They may meet a NO_HZ_FULL enabled kernel soonish, but will be told to
> not turn it on for anything other than pure compute, as NO_HZ_FULL is
> currently not usable for mixed load in partitioned box, much less rt. 

OK, sounds like synchronize_rcu_expedited() is a complete non-problem
for them, then.

							Thanx, Paul

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