From: Thomas Gleixner <tglx@linutronix.de>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Gilad Ben-Yossef <gilad@benyossef.com>, Tejun Heo <tj@kernel.org>,
Mike Frysinger <vapier@gentoo.org>,
Minchan Kim <minchan.kim@gmail.com>,
Hakan Akkan <hakanakkan@gmail.com>,
Max Krasnyansky <maxk@qualcomm.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, hughd@google.com, viresh.kumar@linaro.org,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>
Subject: Re: vmstat: On demand vmstat workers V4
Date: Sat, 10 May 2014 14:31:28 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.02.1405101423360.6261@ionos.tec.linutronix.de> (raw)
In-Reply-To: <20140510004843.GB32393@localhost.localdomain>
On Sat, 10 May 2014, Frederic Weisbecker wrote:
> But I still have the plan to make the timekeeper use the full sysidle
> facility in order to adaptively get to dynticks idle.
>
> Reminder for others: in NO_HZ_FULL, the timekeeper (always CPU 0) stays
> completely periodic. It can't enter in dynticks idle mode because it
> must maintain timekeeping on behalf of full dynticks CPUs. So that's
> a power issue.
>
> But Paul has a feature in RCU that lets us know when all CPUs are idle
> and the timekeeper can finally sleep. Then when a full nohz CPU wakes
> up from idle, it sends an IPI to the timekeeper if needed so the latter
> restarts timekeeping maintainance.
>
> It's not complicated to add to the timer code.
> Most of the code is already there, in RCU, for a while already.
>
> Are we keeping that direction?
So the idea is that the timekeeper stays on cpu0, but if everything is
idle it is allowed to take a long nap as well. So if some other cpu
wakes up it updates timekeeping without taking over the time keeper
duty and if it has work to do, it kicks cpu0 into gear. If it just
goes back to sleep, then nothing to do.
No objections from my side.
Thanks,
tglx
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2014-05-10 12:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 15:35 Christoph Lameter
2014-05-08 21:29 ` Andrew Morton
2014-05-08 22:18 ` Thomas Gleixner
2014-05-09 14:53 ` Christoph Lameter
2014-05-09 15:05 ` Thomas Gleixner
2014-05-09 15:28 ` Christoph Lameter
2014-05-09 22:57 ` Thomas Gleixner
2014-05-09 23:47 ` Paul E. McKenney
2014-05-10 0:48 ` Frederic Weisbecker
2014-05-10 12:31 ` Thomas Gleixner [this message]
2014-05-10 13:14 ` Frederic Weisbecker
2014-05-11 1:17 ` Paul E. McKenney
2014-05-11 1:30 ` Frederic Weisbecker
2014-05-11 1:38 ` Paul E. McKenney
2014-05-10 12:20 ` Thomas Gleixner
2014-05-11 1:12 ` Paul E. McKenney
2014-05-10 0:34 ` Frederic Weisbecker
2014-05-10 12:22 ` Thomas Gleixner
2014-05-11 1:14 ` Paul E. McKenney
2014-05-12 16:25 ` Christoph Lameter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.02.1405101423360.6261@ionos.tec.linutronix.de \
--to=tglx@linutronix.de \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=fweisbec@gmail.com \
--cc=gilad@benyossef.com \
--cc=hakanakkan@gmail.com \
--cc=hpa@zytor.com \
--cc=hughd@google.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=maxk@qualcomm.com \
--cc=minchan.kim@gmail.com \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=tj@kernel.org \
--cc=vapier@gentoo.org \
--cc=viresh.kumar@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox