Message-ID: <1502735386.31351.61.camel@gmx.de>
Subject: Re: [RFC PATCH 7/9] housekeeping: Use own boot option, independant
 from nohz
From: Mike Galbraith <efault@gmx.de>
To: Luiz Capitulino <lcapitulino@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Chris Metcalf <cmetcalf@mellanox.com>,
        Thomas Gleixner <tglx@linutronix.de>, Christoph Lameter <cl@linux.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>,
        Wanpeng Li <kernellwp@gmail.com>
Date: Mon, 14 Aug 2017 20:29:46 +0200
In-Reply-To: <20170814133440.3dc31bad@redhat.com>
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         <20170813111340.0ade6d58@redhat.com> <20170814170107.GA27479@lerouge>
         <20170814133440.3dc31bad@redhat.com>
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On Mon, 2017-08-14 at 13:34 -0400, Luiz Capitulino wrote:
> On Mon, 14 Aug 2017 19:01:09 +0200
> 
> > What is the source of the load balancing inducing such latency when a single
> > task is affine to a CPU? If this is idle load balancing, it is now affine to
> > housekeepers. If this is task wakeup then it's suprising because select_task_rq()
> > is optimized toward single CPU affinity.
> 
> I guess it was idle load balancing, but I don't remember because this
> was a few years ago. I think this might be reproducible without using
> isolcpus=. I'll give it a try shortly and let you know.

idle_balance() can swamp other noise by a couple orders of magnitude,

	-Mike