From: Peter Zijlstra <peterz@infradead.org>
To: Prarit Bhargava <prarit@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Len Brown <len.brown@intel.com>, Borislav Petkov <bp@suse.de>,
Andi Kleen <ak@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>,
Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH 2/2] cpu hotplug, add CONFIG_PERMANENT_CPU_TOPOLOGY
Date: Thu, 8 Sep 2016 09:45:42 +0200 [thread overview]
Message-ID: <20160908074542.GY10138@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1473248657-17359-3-git-send-email-prarit@redhat.com>
On Wed, Sep 07, 2016 at 07:44:17AM -0400, Prarit Bhargava wrote:
> The information in /sys/devices/system/cpu/cpuX/topology
> directory is useful for userspace monitoring applications and in-tree
> utilities like cpupower & turbostat.
>
> When down'ing a CPU the /sys/devices/system/cpu/cpuX/topology directory is
> removed during the CPU_DEAD hotplug callback in the kernel. The problem
> with this model is that the CPU has not been physically removed and the
> data in the topology directory is still valid and the cpu's location is
> now lost to userspace.
>
> This patch adds CONFIG_PERMANENT_CPU_TOPOLOGY, and is Y by default for
> x86, an N for all other arches. When enabled the kernel is modified so
> that the topology directory is added to the core cpu sysfs files so that
> the topology directory exists while the CPU is physically present. When
> disabled, the behavior of the current kernel is maintained (that is, the
> topology directory is removed on a soft down and added on an soft up).
> Adding CONFIG_PERMANENT_CPU_TOPOLOGY may require additional architecture
> so that the cpumask data the CPU's topology is not cleared during a CPU
> down.
So how do you physically remove things and how does the information then
get removed?
Also, why is that an x86 only feature?
next prev parent reply other threads:[~2016-09-08 7:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-07 11:44 [PATCH 0/2] cpu hotplug, keep topology directory after soft remove event Prarit Bhargava
2016-09-07 11:44 ` [PATCH 1/2] drivers/base: Combine topology.c and cpu.c Prarit Bhargava
2016-09-07 13:31 ` kbuild test robot
2016-09-07 11:44 ` [PATCH 2/2] cpu hotplug, add CONFIG_PERMANENT_CPU_TOPOLOGY Prarit Bhargava
2016-09-08 7:45 ` Peter Zijlstra [this message]
2016-09-08 13:45 ` Prarit Bhargava
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=20160908074542.GY10138@twins.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=ak@linux.intel.com \
--cc=bp@suse.de \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=jolsa@redhat.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=prarit@redhat.com \
--cc=tglx@linutronix.de \
--cc=x86@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
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;
as well as URLs for NNTP newsgroup(s).