linux-kernel - Re: TREE_SRCU slows hotplug by factor ~16

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Message-Id: <20170427041136.GA3956@linux.vnet.ibm.com>
Date:   Wed, 26 Apr 2017 21:11:36 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Mike Galbraith <efault@....de>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: TREE_SRCU slows hotplug by factor ~16

On Thu, Apr 27, 2017 at 05:43:59AM +0200, Mike Galbraith wrote:
> On Wed, 2017-04-26 at 20:12 +0200, Mike Galbraith wrote:
> > On Wed, 2017-04-26 at 10:56 -0700, Paul E. McKenney wrote:
> > 
> > > > OK, I do need to do more work.  My current guess is that I should have
> > > > set the default for srcutree.exp_holdoff to 25*1000 instead of 50*1000.
> > > > But I am sure that further data will show me the error of my ways.  ;-)
> > 
> > I can give that a go tomorrow (too crispy now).
> 
> real    0m39.177s
> user    0m0.225s
> sys     0m5.344s
> 
> tadaaa  (tricorder noises... it's dead Jim)

This is with srcutree.exp_holdoff set to 25*1000?  If so, great news!
Really easy to adjust the default.  ;-)

							Thanx, Paul