Re: RFC: Getting rid of LTR in VMX

From	hpa@zytor.com
Newsgroups	linux.kernel
Subject	Re: RFC: Getting rid of LTR in VMX
Date	2017-02-20 23:30 +0100
Message-ID	<td4D0-26B-13@gated-at.bofh.it> (permalink)
References	(1 earlier) <tcU0W-3Tt-17@gated-at.bofh.it> <tcZjY-77l-13@gated-at.bofh.it> <tcZtE-7aS-17@gated-at.bofh.it> <tcZDk-7to-1@gated-at.bofh.it> <td4jD-1Zp-21@gated-at.bofh.it>
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On February 20, 2017 2:02:53 PM PST, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>> > Yes.  But 150-200 clock cycles are nothing compared to the cache
>misses
>> > you get from preemption, so I'd ignore that.  Saving 300 clock
>cycles on
>> > userspace exits from TR+GSBASE would be about 5% on my Haswell.
>> 
>> That's still 5% :)
>
>Yes, 5% on userspace exits is good (though they're rare).
>
>OTOH, 300 clock cycles on preemption are nothing to write home about.
>
>Paolo

Oh, I would say it is... especially when it's basically free.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

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Thread

RFC: Getting rid of LTR in VMX Andy Lutomirski <luto@amacapital.net> - 2017-02-18 04:40 +0100
  Re: RFC: Getting rid of LTR in VMX Paolo Bonzini <pbonzini@redhat.com> - 2017-02-18 16:20 +0100
  Re: RFC: Getting rid of LTR in VMX Paolo Bonzini <pbonzini@redhat.com> - 2017-02-20 12:10 +0100
    Re: RFC: Getting rid of LTR in VMX Andy Lutomirski <luto@amacapital.net> - 2017-02-20 17:50 +0100
      Re: RFC: Getting rid of LTR in VMX Paolo Bonzini <pbonzini@redhat.com> - 2017-02-20 18:00 +0100
        Re: RFC: Getting rid of LTR in VMX Andy Lutomirski <luto@amacapital.net> - 2017-02-20 18:10 +0100
          Re: RFC: Getting rid of LTR in VMX Paolo Bonzini <pbonzini@redhat.com> - 2017-02-20 23:10 +0100
            Re: RFC: Getting rid of LTR in VMX hpa@zytor.com - 2017-02-20 23:30 +0100

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