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Subject: Re: [lkp] [x86/hweight]  65ea11ec6a:  will-it-scale.per_process_ops 9.3% improvement
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Tue, 16 Aug 2016 16:09:19 -0700
To: Borislav Petkov <bp@suse.de>
CC: kernel test robot <xiaolong.ye@intel.com>,
        =?ISO-8859-1?Q?Ville_Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>, Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
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On August 16, 2016 10:16:35 AM PDT, Borislav Petkov <bp@suse.de> wrote:
>On Tue, Aug 16, 2016 at 09:59:00AM -0700, H. Peter Anvin wrote:
>> Dang...
>
>Isn't 9.3% improvement a good thing(tm) ?

Yes, it's huge.  The only explanation I could imagine is that scrambling %rdi caused the scheduler to do completely the wrong thing.
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