Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event
Date	2016-09-27 14:00 +0200
Message-ID	<slZdf-D0-13@gated-at.bofh.it> (permalink)
References	(4 earlier) <skaPw-5PF-41@gated-at.bofh.it> <skb8S-6eS-11@gated-at.bofh.it> <slCA2-3kx-5@gated-at.bofh.it> <slCTo-3FS-11@gated-at.bofh.it> <slZ3z-zK-5@gated-at.bofh.it>
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On Tue, Sep 27, 2016 at 07:47:56AM -0400, Prarit Bhargava wrote:

> There's a difference between soft remove (via sysfs) and a true hot remove
> operation (where the whole thing is physically removed).  Soft remove only
> results in the processor being made "not available" to the scheduler.

How is it different? We do _ONE_ CPU unplug operation. We do not touch
the thing anymore after that. It _can_ be taken out after that.

Therefore hotplug wipes the topology information and clears the CPU from
relevant bitmasks.

From the kernel's POV there really is no distinction.

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Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Prarit Bhargava <prarit@redhat.com> - 2016-09-26 13:50 +0200
  Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Borislav Petkov <bp@suse.de> - 2016-09-26 14:00 +0200
    Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Prarit Bhargava <prarit@redhat.com> - 2016-09-27 13:50 +0200
      Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-09-27 16:00 +0200
        Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Prarit Bhargava <prarit@redhat.com> - 2016-09-27 17:30 +0200
          Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Borislav Petkov <bp@suse.de> - 2016-09-28 07:10 +0200
          Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Peter Zijlstra <peterz@infradead.org> - 2016-09-28 08:50 +0200
            Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Prarit Bhargava <prarit@redhat.com> - 2016-09-28 12:10 +0200
      Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Borislav Petkov <bp@suse.de> - 2016-09-28 07:10 +0200
  Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Peter Zijlstra <peterz@infradead.org> - 2016-09-26 14:10 +0200
    Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Prarit Bhargava <prarit@redhat.com> - 2016-09-27 13:50 +0200
      Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after  soft remove event Peter Zijlstra <peterz@infradead.org> - 2016-09-27 14:00 +0200

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