From: Ingo Molnar <mingo@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Vatika Harlalka <vatikaharlalka@gmail.com>,
Chris Metcalf <cmetcalf@ezchip.com>,
Thomas Gleixner <tglx@linutronix.de>,
Preeti U Murthy <preeti@linux.vnet.ibm.com>,
Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers
Date: Tue, 25 Aug 2015 10:29:04 +0200 [thread overview]
Message-ID: <20150825082904.GA20562@gmail.com> (raw)
In-Reply-To: <20150824133559.GA27147@lerouge>
* Frederic Weisbecker <fweisbec@gmail.com> wrote:
> On Mon, Aug 24, 2015 at 08:44:12AM +0200, Ingo Molnar wrote:
> > 2)
> >
> > What happens if the boot CPU is offlined? (under CONFIG_BOOTPARAM_HOTPLUG_CPU0=y)
> >
> > I don't see CPU hotplug callbacks fixing up the housekeeping_mask if the boot CPU
> > is offlined.
>
> We have tick_nohz_cpu_down_callback() which makes sure that the timekeeper, which
> is the boot CPU in nohz full, never gets offlined.
That solution really sucks - it essentially regresses a feature the user
explicitly asked for! I also see no way for the user to migrate the timekeeping
functionality over to another CPU without rebooting.
If this is the last timekeeping CPU then it should migrate the timekeeping
functionality to another CPU, and perhaps printk a warning if all other CPUs are
nohz-full and we have to mark one of them as the timekeeper.
Also, the nohz-full and timekeeper functionality should not be a boot parameter
only thing, but should be runtime configurable.
Thanks,
Ingo
next prev parent reply other threads:[~2015-08-25 8:29 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-14 1:46 [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers Frederic Weisbecker
2015-08-22 21:09 ` Ping: " Frederic Weisbecker
2015-08-23 1:22 ` Christoph Lameter
2015-08-23 5:40 ` Ingo Molnar
2015-08-23 16:01 ` Paul E. McKenney
2015-08-24 1:28 ` Frederic Weisbecker
2015-08-24 6:44 ` Ingo Molnar
2015-08-24 7:23 ` Mike Galbraith
2015-08-24 7:41 ` Ingo Molnar
2015-08-24 7:54 ` Mike Galbraith
2015-08-24 8:00 ` Ingo Molnar
2015-08-24 13:36 ` Frederic Weisbecker
2015-08-24 14:01 ` Mike Galbraith
2015-08-25 8:29 ` Ingo Molnar [this message]
2015-08-25 13:45 ` Frederic Weisbecker
2015-08-28 8:32 ` Ingo Molnar
2015-08-28 12:30 ` Frederic Weisbecker
2015-08-24 13:50 ` Paul E. McKenney
2015-08-24 14:04 ` Frederic Weisbecker
2015-08-24 15:45 ` Paul E. McKenney
2015-08-24 1:45 ` Frederic Weisbecker
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=20150825082904.GA20562@gmail.com \
--to=mingo@kernel.org \
--cc=cl@linux.com \
--cc=cmetcalf@ezchip.com \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=preeti@linux.vnet.ibm.com \
--cc=tglx@linutronix.de \
--cc=vatikaharlalka@gmail.com \
/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