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

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Date:   Wed, 26 Apr 2017 22:32:28 -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 06:15:56AM +0200, Mike Galbraith wrote:
> On Wed, 2017-04-26 at 21:11 -0700, Paul E. McKenney wrote:
> 
> > This is with srcutree.exp_holdoff set to 25*1000?
> 
> Yup.

And please see below for the trivial patch, just for confirmation.
May I add your Tested-by?

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index ccbe1fb84165..65f03bca5b32 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -39,7 +39,7 @@

 #include "rcu.h"

-ulong exp_holdoff = 50 * 1000; /* Holdoff (ns) for auto-expediting. */
+ulong exp_holdoff = 25 * 1000; /* Holdoff (ns) for auto-expediting. */
 module_param(exp_holdoff, ulong, 0444);

 static void srcu_invoke_callbacks(struct work_struct *work);