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

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Message-ID: <20160818041139.GA22101@nazgul.tnic>
Date:	Thu, 18 Aug 2016 06:11:39 +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 08:54:11PM -0700, Huang, Ying wrote:
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic
> popcnt tsc_deadline_timer aes xsave avx lahf_lm tpr_shadow vnmi flexpriority ept vpid xsaveopt dtherm ida arat pln pts
  ^^^^^^

There it is.

So if there's no bug, alternatives should replace all "call
__sw_hweightXX" calls with POPCNT. So you shouldn't be even calling
these functions and hitting that path.

Can you boot the kernel with "debug-alternative" and put that dmesg
somewhere along with vmlinux for me to stare at? Privately is fine too.

I'd like to make sure the alternatives application actually happens.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

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