Linux-csky Archive on lore.kernel.org
 help / color / Atom feed
From: Hsin-Yi Wang <hsinyi@chromium.org>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Kosina <jkosina@suse.cz>,
	Pavankumar Kondeti <pkondeti@codeaurora.org>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Aaro Koskinen <aaro.koskinen@nokia.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Will Deacon <will@kernel.org>, Fenghua Yu <fenghua.yu@intel.com>,
	James Morse <james.morse@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Guenter Roeck <groeck@chromium.org>,
	Stephen Boyd <swboyd@chromium.org>,
	lkml <linux-kernel@vger.kernel.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	linux-csky@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	linux-s390@vger.kernel.org,
	Linux-sh list <linux-sh@vger.kernel.org>,
	sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [PATCH v5] reboot: support offline CPUs before reboot
Date: Thu, 16 Jan 2020 17:25:43 +0800
Message-ID: <CAJMQK-ip7C71=K+CViEKcc3ed4GPY_Uknm5uNgLJTzZb2aQOcA@mail.gmail.com> (raw)
In-Reply-To: <20200115114112.GA3663@bogus>

On Wed, Jan 15, 2020 at 7:41 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> On Wed, Jan 15, 2020 at 02:34:10PM +0800, Hsin-Yi Wang wrote:
> > Currently system reboots uses architecture specific codes (smp_send_stop)
> > to offline non reboot CPUs. Most architecture's implementation is looping
> > through all non reboot online CPUs and call ipi function to each of them. Some
> > architecture like arm64, arm, and x86... would set offline masks to cpu without
> > really offline them. This causes some race condition and kernel warning comes
> > out sometimes when system reboots.
> >
> > This patch adds a config ARCH_OFFLINE_CPUS_ON_REBOOT, which would offline cpus in
> > migrate_to_reboot_cpu(). If non reboot cpus are all offlined here, the loop for
> > checking online cpus would be an empty loop. If architecture don't enable this
> > config, or some cpus somehow fails to offline, it would fallback to ipi
> > function.
> >
>
> What's the timing impact on systems with large number of CPUs(say 256 or
> more) ? I remember we added some change to reduce the wait times for
> offlining CPUs in system suspend path on arm64, still not negligible.
>

This is not the final solution, but I would still provided some data
points here:

Tested on my arm64 with 4 cpu: 2 a53 and 2 a72.
Offlining 3 cpu takes about 60~65 ms
Offlining 2 cpu(a53+a72 or a72+a72) takes about 42~47 ms
Offlining 1 cpu(a53 or a72) takes about 23~25 ms.

It would take longer time for systems with large number of CPUs.

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15  6:34 Hsin-Yi Wang
2020-01-15  9:49 ` Rafael J. Wysocki
2020-01-15 11:34   ` Hsin-Yi Wang
2020-01-15 11:41 ` Sudeep Holla
2020-01-16  9:25   ` Hsin-Yi Wang [this message]
2020-01-16  0:30 ` Thomas Gleixner
2020-01-16  9:18   ` Hsin-Yi Wang
2020-01-16 11:10     ` Thomas Gleixner

Reply instructions:

You may reply publically 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='CAJMQK-ip7C71=K+CViEKcc3ed4GPY_Uknm5uNgLJTzZb2aQOcA@mail.gmail.com' \
    --to=hsinyi@chromium.org \
    --cc=aaro.koskinen@nokia.com \
    --cc=fenghua.yu@intel.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=groeck@chromium.org \
    --cc=heiko.carstens@de.ibm.com \
    --cc=james.morse@arm.com \
    --cc=jkosina@suse.cz \
    --cc=jpoimboe@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-csky@vger.kernel.org \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mips@vger.kernel.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=linux-sh@vger.kernel.org \
    --cc=linux-xtensa@linux-xtensa.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mark.rutland@arm.com \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=pkondeti@codeaurora.org \
    --cc=sparclinux@vger.kernel.org \
    --cc=sudeep.holla@arm.com \
    --cc=swboyd@chromium.org \
    --cc=tglx@linutronix.de \
    --cc=vkuznets@redhat.com \
    --cc=will@kernel.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

Linux-csky Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-csky/0 linux-csky/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-csky linux-csky/ https://lore.kernel.org/linux-csky \
		linux-csky@vger.kernel.org
	public-inbox-index linux-csky

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-csky


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git