linux-kernel - Re: [LKP] [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process

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Message-ID: <20160818034513.GA21415@nazgul.tnic>
Date:	Thu, 18 Aug 2016 05:45:13 +0200
From:	Borislav Petkov <bp@...e.de>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Brian Gerst <brgerst@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>, lkp@...org,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Subject: Re: [LKP] [lkp] [x86/hweight] 65ea11ec6a:
 will-it-scale.per_process_ops 9.3% improvement

On Wed, Aug 17, 2016 at 03:29:04PM -0700, Huang, Ying wrote:
> branch-miss-rate decreased from ~0.30% to ~0.043%.
> 
> So I guess there are some code alignment change, which caused decreased
> branch miss rate.

Hrrm, I still can't imagine how that would happen if the machine
supports POPCNT and we never call the __sw_hweight* variants. Or does
it?

Can you paste /proc/cpuinfo from that Sandy Bridge-EP box?

Thanks.

-- 
Regards/Gruss,
    Boris.

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