From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@suse.de>, "Huang, Ying" <ying.huang@intel.com>
Cc: "Denys Vlasenko" <dvlasenk@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Brian Gerst" <brgerst@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"Andy Lutomirski" <luto@amacapital.net>,
lkp@01.org, "Thomas Gleixner" <tglx@linutronix.de>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Ville Syrjälä" <ville.syrjala@linux.intel.com>
Subject: Re: [LKP] [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement
Date: Wed, 17 Aug 2016 20:57:12 -0700 [thread overview]
Message-ID: <ABE9E34B-8A07-4A82-B7A0-BA340FE2C6B2@zytor.com> (raw)
In-Reply-To: <20160818034513.GA21415@nazgul.tnic>
On August 17, 2016 8:45:13 PM PDT, Borislav Petkov <bp@suse.de> wrote:
>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.
popcnt was introduced in Nehalem AFAIK, two generations before Sandy Bridge.
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
next prev parent reply other threads:[~2016-08-18 3:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-16 14:26 [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement kernel test robot
2016-08-16 16:59 ` H. Peter Anvin
2016-08-16 17:16 ` Borislav Petkov
2016-08-16 23:09 ` H. Peter Anvin
2016-08-17 5:46 ` Borislav Petkov
2016-08-17 22:29 ` [LKP] " Huang, Ying
2016-08-18 3:45 ` Borislav Petkov
2016-08-18 3:54 ` Huang, Ying
2016-08-18 4:11 ` Borislav Petkov
2016-08-25 9:22 ` Borislav Petkov
2016-08-25 10:05 ` H. Peter Anvin
2016-08-25 11:45 ` Borislav Petkov
2016-08-25 20:07 ` H. Peter Anvin
2016-08-18 3:57 ` H. Peter Anvin [this message]
2016-08-17 6:48 ` Peter Zijlstra
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