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From: Frederic Weisbecker <fweisbec@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Rob Landley <rob@landley.net>,
	linux-kernel@vger.kernel.org, josh@joshtriplett.org,
	zhong@linux.vnet.ibm.com, khilman@linaro.org,
	geoff@infradead.org, tglx@linutronix.de
Subject: Re: [PATCH] nohz1: Documentation
Date: Mon, 25 Mar 2013 15:37:30 +0100	[thread overview]
Message-ID: <CAFTL4hzFmrHPHhi3gBj05eJgxb5H7bACEWwCm7jp6Vb0XU15bA@mail.gmail.com> (raw)
In-Reply-To: <0000013da1f6170e-7b247826-93a9-4c2d-a316-ba3b0597a805-000000@email.amazonses.com>

2013/3/25 Christoph Lameter <cl@linux.com>:
> On Fri, 22 Mar 2013, Paul E. McKenney wrote:
>
>> On Fri, Mar 22, 2013 at 02:38:58PM +0000, Christoph Lameter wrote:
>> > On Thu, 21 Mar 2013, Paul E. McKenney wrote:
>> >
>> > > So, how long of busy periods are you contemplating for your SCHED_FIFO
>> > > threads?  Is it possible to tune/adjust the offending per-CPU ktheads
>> > > to wake up less frequently than that time?
>> >
>> > Test programs right now run 10 seconds. 30 seconds would definitely be
>> > enough for the worst case.
>>
>> OK, that might be doable for some workloads.  What happens when you
>> try tuning the 2-second wakeup interval to (say) 45 seconds?
>
> The vm kernel threads do no useful work if no system calls are being done.
> If there is no kernel action then they can be deferred indefinitely.
>

We can certainly add some user deferrable timer_list. But that's going
to be for extreme usecases (those who require pure isolation) because
we'll need to settle that with a timer reprogramming into user/kernel
boundaries. That won't be free.

  reply	other threads:[~2013-03-25 14:37 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-18 16:29 [PATCH] nohz1: Documentation Paul E. McKenney
2013-03-18 18:13 ` Rob Landley
2013-03-18 18:46   ` Frederic Weisbecker
2013-03-18 19:59     ` Rob Landley
2013-03-18 20:48       ` Frederic Weisbecker
2013-03-18 22:25         ` Paul E. McKenney
2013-03-20 23:32           ` Steven Rostedt
2013-03-20 23:55             ` Paul E. McKenney
2013-03-21  0:27               ` Steven Rostedt
2013-03-21  2:22                 ` Paul E. McKenney
2013-03-21 10:16                   ` Borislav Petkov
2013-03-21 15:18                     ` Paul E. McKenney
2013-03-21 16:00                       ` Borislav Petkov
2013-03-21 15:45                 ` Arjan van de Ven
2013-03-21 17:18                   ` Paul E. McKenney
2013-03-21 17:41                     ` Arjan van de Ven
2013-03-21 18:02                       ` Paul E. McKenney
2013-03-22 18:37                         ` Kevin Hilman
2013-03-22 19:25                           ` Paul E. McKenney
2013-03-22  4:59                   ` Rob Landley
2013-03-21 18:01                 ` Frederic Weisbecker
2013-03-21 18:26                   ` Paul E. McKenney
2013-03-21 16:08               ` Christoph Lameter
2013-03-21 17:15                 ` Paul E. McKenney
2013-03-21 18:39                   ` Christoph Lameter
2013-03-21 18:58                     ` Paul E. McKenney
2013-03-21 20:04                       ` Christoph Lameter
2013-03-21 20:42                         ` Frederic Weisbecker
2013-03-21 21:02                           ` Christoph Lameter
2013-03-21 21:06                             ` Frederic Weisbecker
2013-03-21 20:50                         ` Paul E. McKenney
2013-03-22 14:38                           ` Christoph Lameter
2013-03-22 16:28                             ` Paul E. McKenney
2013-03-25 14:31                               ` Christoph Lameter
2013-03-25 14:37                                 ` Frederic Weisbecker [this message]
2013-03-25 15:18                                   ` Christoph Lameter
2013-03-25 15:20                                     ` Frederic Weisbecker
2013-03-22  9:52                         ` Mats Liljegren
2013-03-22 19:01                       ` Kevin Hilman
2013-03-21 18:44                   ` Steven Rostedt
2013-03-21 18:53                     ` Christoph Lameter
2013-03-21 19:16                       ` Steven Rostedt
2013-03-21 18:59                     ` Paul E. McKenney

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