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

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Date:   Mon, 24 Apr 2017 07:24:44 +0200
From:   Mike Galbraith <efault@....de>
To:     paulmck@...ux.vnet.ibm.com
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: TREE_SRCU slows hotplug by factor ~16

On Sun, 2017-04-23 at 20:32 -0700, Paul E. McKenney wrote:
> On Mon, Apr 24, 2017 at 04:48:09AM +0200, Mike Galbraith wrote:
> > Greetings,
> > 
> > Running Steven's hotplug stress script in tip w. CLASSIC_SRCU takes 55s
> > in my i4790 box, whereas TREE_SRCU takes over 16m.  (Master with the
> > same config does it in 39s.. but then lockdep isn't enabled in master)
> 
> That doesn't sound good...
> 
> But exactly which version are you using?  There were some 8x slowdowns
> earlier this week that have since been fixed.  Also, how many CPUs are
> on your system?

4 cores+SMT, tip.yesterday_afternoon (precise!) was initial test point,
tip.this_morning (v4.11-rc7-955-g76f8909e1cd8) is still slow.

	-Mike