From: Borislav Petkov <bp@suse.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "kernel test robot" <xiaolong.ye@intel.com>,
"Ville Syrjälä" <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>,
LKML <linux-kernel@vger.kernel.org>,
lkp@01.org
Subject: Re: [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement
Date: Wed, 17 Aug 2016 07:46:05 +0200 [thread overview]
Message-ID: <20160817054605.GA6728@nazgul.tnic> (raw)
In-Reply-To: <796A2A72-06B7-4B3D-AA38-DF558FC75857@zytor.com>
On Tue, Aug 16, 2016 at 04:09:19PM -0700, H. Peter Anvin wrote:
> 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.
I'm questioning the validity, actually. Report says test machine was
Sandy Bridge-EP and I'd bet good money this one has POPCNT support so
how are we even hitting that __sw_hweight64() path, at all?
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--
next prev parent reply other threads:[~2016-08-17 5:47 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 [this message]
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
2016-08-17 6:48 ` Peter Zijlstra
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