linux-kernel - Re: [PATCH tip/core/rcu 02/15] rcu: Use timer as backstop for NOCB deferred wakeups

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Message-Id: <20170727173351.GF3730@linux.vnet.ibm.com>
Date:   Thu, 27 Jul 2017 10:33:51 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com
Subject: Re: [PATCH tip/core/rcu 02/15] rcu: Use timer as backstop for NOCB
 deferred wakeups

On Wed, Jul 26, 2017 at 07:09:34PM -0400, Steven Rostedt wrote:
> On Wed, 26 Jul 2017 14:47:41 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> 
> > > It is much lighter weight than a timer setup.  
> > 
> > How much lighter weight?  In other words, what fraction of the
> > timers have to avoid being cancelled for irq_work to break even?
> 
> No idea. I guess that would be a nice academic exercise ;-)

Hmmm...  I guess I should try it and see what it does, though that
would be some merge window after the upcoming one.  If it is indeed
simpler, I might forgive some possible performance shortcomings...

							Thanx, Paul