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Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock

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On Mon, 04 Sep 2017, Peter Zijlstra wrote:

>For testing its trivial to hack your kernel and I don't feel this is
>something an Admin can make reasonable decisions about.
>
>So why? In general less knobs is better.

+1.

Also, note how b8fa70b51aa (xen, pvticketlocks: Add xen_nopvspin parameter
to disable xen pv ticketlocks) has no justification as to why its wanted
in the first place. The only thing I could find was from 15a3eac0784
(xen/spinlock: Document the xen_nopvspin parameter):

"Useful for diagnosing issues and comparing benchmarks in over-commit CPU scenarios."

So I vote for no additional knobs, specially for such core code.

Thanks,
Davidlohr

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[PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock Oscar Salvador <osalvador@suse.de> - 2017-09-04 16:40 +0200
  Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-04 16:50 +0200
    Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Waiman Long <longman@redhat.com> - 2017-09-04 21:40 +0200
    Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Davidlohr Bueso <dave@stgolabs.net> - 2017-09-05 00:30 +0200
      Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Juergen Gross <jgross@suse.com> - 2017-09-05 08:30 +0200
        Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-05 09:00 +0200
          Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Juergen Gross <jgross@suse.com> - 2017-09-05 09:40 +0200
            Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Juergen Gross <jgross@suse.com> - 2017-09-05 10:20 +0200
              Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-05 10:30 +0200
                Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Juergen Gross <jgross@suse.com> - 2017-09-05 11:00 +0200
                Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-05 11:10 +0200
                Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Juergen Gross <jgross@suse.com> - 2017-09-05 11:20 +0200
            Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-05 10:20 +0200
        Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Oscar Salvador <osalvador@suse.de> - 2017-09-05 09:00 +0200
          Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV  spinlock Peter Zijlstra <peterz@infradead.org> - 2017-09-05 10:10 +0200

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