From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org,
Petr Mladek <pmladek@suse.com>,
Chris Metcalf <cmetcalf@mellanox.com>,
open list <linux-kernel@vger.kernel.org>,
Aaron Tomlin <atomlin@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] ARM: smp: Remove CPU: shutdown notice
Date: Tue, 17 Jan 2017 23:23:14 +0000 [thread overview]
Message-ID: <20170117232314.GI27312@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20170117230714.6799-1-f.fainelli@gmail.com>
On Tue, Jan 17, 2017 at 03:07:12PM -0800, Florian Fainelli wrote:
> This message is not particularly informative, and is not paired with an
> identical message when a CPU is brought online. Finally, it slows the
> CPU hotplug path down, thus allowing less CPU hotplug operations per
> second. Just remove it.
CPU hotplug isn't a fast operation anyway - it's also fairly disruptive
in that it uses stop_machine() to halt activity everywhere while taking
the CPU offline.
If you're worried about a single printk slowing things down, it sounds
like you're doing something wrong here - maybe you should be using
cpuidle for power management rather than trying to make CPU hotplug do
that for you?
A rapidly changing CPU hotplug state has other side effects - such as
reading /proc/interrupts is meaningless, because as soon as you've read
it the CPUs could have changed. It also makes a farce of spreading
interrupts over the available CPUs.
All in all, I don't think this is a good idea...
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2017-01-17 23:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-17 23:07 [PATCH] ARM: smp: Remove CPU: shutdown notice Florian Fainelli
2017-01-17 23:23 ` Russell King - ARM Linux [this message]
2017-01-17 23:39 ` Florian Fainelli
2017-01-18 9:55 ` Petr Mladek
2017-01-18 19:56 ` Florian Fainelli
2017-01-19 12:07 ` Sergey Senozhatsky
2017-01-18 22:39 ` Russell King - ARM Linux
2017-01-18 22:49 ` Florian Fainelli
2017-01-18 22:53 ` [PATCH] ARM: Reduce "CPU: shutdown" message to debug level Florian Fainelli
2017-01-18 23:20 ` Russell King - ARM Linux
2017-01-19 0:27 ` Florian Fainelli
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