From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Anton Blanchard <anton@au1.ibm.com>, Avi Kivity <avi@redhat.com>,
Ingo Molnar <mingo@elte.hu>, Lai Jiangshan <laijs@cn.fujitsu.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Paul Menage <menage@google.com>,
Stephen Hemminger <shemminger@vyatta.com>,
Thomas Gleixner <tglx@linutronix.de>,
Tim Pepper <lnxninja@linux.vnet.ibm.com>
Subject: Re: [PATCH 05/32] nohz: Move rcu dynticks idle mode handling to idle enter/exit APIs
Date: Tue, 30 Aug 2011 13:21:55 +0200 [thread overview]
Message-ID: <1314703315.2799.5.camel@twins> (raw)
In-Reply-To: <20110829233521.GK9748@somewhere.redhat.com>
On Tue, 2011-08-30 at 01:35 +0200, Frederic Weisbecker wrote:
> > That means it has to be in an extended grace period when we stop the
> > tick.
>
> You mean extended quiescent state?
Yeah that :-)
> As a summary here is what we do:
>
> - if we are in the kernel, we can't run into extended quiescent state because
> we may make use of rcu anytime there. But if we run nohz we don't have the tick
> to notice quiescent states to the RCU machinery and help completing grace periods
> so as soon as we receive an rcu IPI from another CPU (due to the grace period
> beeing extended because our nohz CPU doesn't report quiescent states), we restart
> the tick. We are optimistic enough to consider that we may avoid a lot of ticks
> even if there are some risks to be disturbed in some random rates.
> So even with the IPI we consider it as an upside.
>
> - if we are in userspace we can run in extended quiescent state.
But you can only disable the tick/enter extended quiescent state while
in kernel-space. Thus the second clause is precluded from ever being
true.
next prev parent reply other threads:[~2011-08-30 11:22 UTC|newest]
Thread overview: 139+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-15 15:51 [RFC PATCH 00/32] Nohz cpusets (was: Nohz Tasks) Frederic Weisbecker
2011-08-15 15:51 ` [PATCH 01/32 RESEND] nohz: Drop useless call in tick_nohz_start_idle() Frederic Weisbecker
2011-08-29 14:23 ` Peter Zijlstra
2011-08-29 17:10 ` Frederic Weisbecker
2011-08-15 15:51 ` [PATCH 02/32 RESEND] nohz: Drop ts->idle_active Frederic Weisbecker
2011-08-29 14:23 ` Peter Zijlstra
2011-08-29 16:15 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 03/32 RESEND] nohz: Drop useless ts->inidle check before rearming the tick Frederic Weisbecker
2011-08-29 14:23 ` Peter Zijlstra
2011-08-29 16:58 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 04/32] nohz: Separate idle sleeping time accounting from nohz switching Frederic Weisbecker
2011-08-29 14:23 ` Peter Zijlstra
2011-08-29 16:32 ` Frederic Weisbecker
2011-08-29 17:44 ` Peter Zijlstra
2011-08-29 22:53 ` Frederic Weisbecker
2011-08-29 14:23 ` Peter Zijlstra
2011-08-29 17:01 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 05/32] nohz: Move rcu dynticks idle mode handling to idle enter/exit APIs Frederic Weisbecker
2011-08-29 14:25 ` Peter Zijlstra
2011-08-29 17:11 ` Frederic Weisbecker
2011-08-29 17:49 ` Peter Zijlstra
2011-08-29 17:59 ` Frederic Weisbecker
2011-08-29 18:06 ` Peter Zijlstra
2011-08-29 23:35 ` Frederic Weisbecker
2011-08-30 11:17 ` Peter Zijlstra
2011-08-30 14:11 ` Frederic Weisbecker
2011-08-30 14:13 ` Peter Zijlstra
2011-08-30 14:27 ` Frederic Weisbecker
2011-08-30 11:19 ` Peter Zijlstra
2011-08-30 14:26 ` Frederic Weisbecker
2011-08-30 15:22 ` Peter Zijlstra
2011-08-30 18:45 ` Frederic Weisbecker
2011-08-30 11:21 ` Peter Zijlstra [this message]
2011-08-30 14:32 ` Frederic Weisbecker
2011-08-30 15:26 ` Peter Zijlstra
2011-08-30 15:33 ` Frederic Weisbecker
2011-08-30 15:42 ` Peter Zijlstra
2011-08-30 18:53 ` Frederic Weisbecker
2011-08-30 20:58 ` Peter Zijlstra
2011-08-30 22:24 ` Frederic Weisbecker
2011-08-31 9:17 ` Peter Zijlstra
2011-08-31 13:37 ` Frederic Weisbecker
2011-08-31 14:41 ` Peter Zijlstra
2011-09-01 16:40 ` Paul E. McKenney
2011-09-01 17:13 ` Peter Zijlstra
2011-09-02 1:41 ` Paul E. McKenney
2011-09-02 8:24 ` Peter Zijlstra
2011-09-04 19:37 ` Paul E. McKenney
2011-09-05 14:28 ` Peter Zijlstra
2011-08-15 15:52 ` [PATCH 06/32] nohz: Move idle ticks stats tracking out of nohz handlers Frederic Weisbecker
2011-08-29 14:28 ` Peter Zijlstra
2011-09-06 0:35 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 07/32] nohz: Rename ts->idle_tick to ts->last_tick Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 08/32] nohz: Move nohz load balancer selection into idle logic Frederic Weisbecker
2011-08-29 14:45 ` Peter Zijlstra
2011-09-08 14:08 ` Frederic Weisbecker
2011-09-08 17:16 ` Paul E. McKenney
2011-08-15 15:52 ` [PATCH 09/32] nohz: Move ts->idle_calls into strict " Frederic Weisbecker
2011-08-29 14:47 ` Peter Zijlstra
2011-08-29 17:34 ` Frederic Weisbecker
2011-08-29 17:59 ` Peter Zijlstra
2011-08-29 18:23 ` Frederic Weisbecker
2011-08-29 18:33 ` Peter Zijlstra
2011-08-30 14:45 ` Frederic Weisbecker
2011-08-30 15:33 ` Peter Zijlstra
2011-09-06 16:35 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 10/32] nohz: Move next idle expiring time record into idle logic area Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 11/32] cpuset: Set up interface for nohz flag Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 12/32] nohz: Try not to give the timekeeping duty to a cpuset nohz cpu Frederic Weisbecker
2011-08-29 14:55 ` Peter Zijlstra
2011-08-30 15:17 ` Frederic Weisbecker
2011-08-30 15:30 ` Dimitri Sivanich
2011-08-30 15:37 ` Peter Zijlstra
2011-08-30 22:44 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 13/32] nohz: Adaptive tick stop and restart on nohz cpuset Frederic Weisbecker
2011-08-29 15:25 ` Peter Zijlstra
2011-09-06 13:03 ` Frederic Weisbecker
2011-08-29 15:28 ` Peter Zijlstra
2011-08-29 18:02 ` Frederic Weisbecker
2011-08-29 18:07 ` Peter Zijlstra
2011-08-29 18:28 ` Frederic Weisbecker
2011-08-30 12:44 ` Peter Zijlstra
2011-08-30 14:38 ` Frederic Weisbecker
2011-08-30 15:28 ` Peter Zijlstra
2011-08-29 15:32 ` Peter Zijlstra
2011-08-15 15:52 ` [PATCH 14/32] nohz/cpuset: Don't turn off the tick if rcu needs it Frederic Weisbecker
2011-08-16 20:13 ` Paul E. McKenney
2011-08-17 2:10 ` Frederic Weisbecker
2011-08-17 2:49 ` Paul E. McKenney
2011-08-29 15:36 ` Peter Zijlstra
2011-08-15 15:52 ` [PATCH 15/32] nohz/cpuset: Restart tick when switching to idle task Frederic Weisbecker
2011-08-29 15:43 ` Peter Zijlstra
2011-08-30 15:04 ` Frederic Weisbecker
2011-08-30 15:35 ` Peter Zijlstra
2011-08-15 15:52 ` [PATCH 16/32] nohz/cpuset: Wake up adaptive nohz CPU when a timer gets enqueued Frederic Weisbecker
2011-08-29 15:51 ` Peter Zijlstra
2011-08-29 15:55 ` Peter Zijlstra
2011-08-30 15:06 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 17/32] x86: New cpuset nohz irq vector Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 18/32] nohz/cpuset: Don't stop the tick if posix cpu timers are running Frederic Weisbecker
2011-08-29 15:59 ` Peter Zijlstra
2011-08-15 15:52 ` [PATCH 19/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset Frederic Weisbecker
2011-08-29 16:02 ` Peter Zijlstra
2011-08-30 15:10 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 20/32] nohz/cpuset: Restart the tick if printk needs it Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 21/32] rcu: Restart the tick on non-responding adaptive nohz CPUs Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 22/32] rcu: Restart tick if we enqueue a callback in a nohz/cpuset CPU Frederic Weisbecker
2011-08-16 20:20 ` Paul E. McKenney
2011-08-17 2:18 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 23/32] nohz/cpuset: Account user and system times in adaptive nohz mode Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 24/32] nohz/cpuset: Handle kernel entry/exit to account cputime Frederic Weisbecker
2011-08-16 20:38 ` Paul E. McKenney
2011-08-17 2:30 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 25/32] nohz/cpuset: New API to flush cputimes on nohz cpusets Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 26/32] nohz/cpuset: Flush cputime on threads in nohz cpusets when waiting leader Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 27/32] nohz/cpuset: Flush cputimes on procfs stat file read Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 28/32] nohz/cpuset: Flush cputimes for getrusage() and times() syscalls Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 29/32] x86: Syscall hooks for nohz cpusets Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 30/32] x86: Exception " Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 31/32] rcu: Switch to extended quiescent state in userspace from nohz cpuset Frederic Weisbecker
2011-08-16 20:44 ` Paul E. McKenney
2011-08-17 2:43 ` Frederic Weisbecker
2011-08-15 15:52 ` [PATCH 32/32] nohz/cpuset: Disable under some configs Frederic Weisbecker
2011-08-17 16:36 ` [RFC PATCH 00/32] Nohz cpusets (was: Nohz Tasks) Avi Kivity
2011-08-18 13:25 ` Frederic Weisbecker
2011-08-20 7:45 ` Paul Menage
2011-08-23 16:36 ` Frederic Weisbecker
2011-08-24 14:41 ` Gilad Ben-Yossef
2011-08-30 14:06 ` Frederic Weisbecker
2011-08-31 3:47 ` Mike Galbraith
2011-08-31 9:28 ` Peter Zijlstra
2011-08-31 10:26 ` Mike Galbraith
2011-08-31 10:33 ` Peter Zijlstra
2011-08-31 14:00 ` Gilad Ben-Yossef
2011-08-31 14:26 ` Peter Zijlstra
2011-08-31 14:05 ` Gilad Ben-Yossef
2011-08-31 16:12 ` Mike Galbraith
2011-08-31 13:57 ` Gilad Ben-Yossef
2011-08-31 14:30 ` Peter Zijlstra
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