linux-kernel - Re: Severe performance regression w/ 4.4+ on Android due to cgroup locking changes

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Message-Id: <20160713210857.GA9511@linux.vnet.ibm.com>
Date:	Wed, 13 Jul 2016 14:08:57 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Tejun Heo <tj@...nel.org>, John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Dmitry Shmidt <dimitrysh@...gle.com>,
	Rom Lemarchand <romlem@...gle.com>,
	Colin Cross <ccross@...gle.com>, Todd Kjos <tkjos@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: Severe performance regression w/ 4.4+ on Android due to cgroup
 locking changes

On Wed, Jul 13, 2016 at 10:57:12PM +0200, Peter Zijlstra wrote:
> On Wed, Jul 13, 2016 at 01:52:11PM -0700, Paul E. McKenney wrote:
> > Not a particularly real-time-friendly fix, but certainly a good check
> > on our various assumptions.
> 
> Not only RT, but also HPC and all the other RDMA userspace polling
> freaks ;-)

If Tejun's lglock-like approach doesn't pan out, then it would quite
easy to make a boot parameter that selected expedited vs. non-expedited
behavior.

							Thanx, Paul